Tipperary-born coachman Richard Boland will begin his royal wedding day well before dawn Wednesday when he rises in the royal mews behind Buckingham Palace to muck out the stalls of Lady Penelope and Krestel. They are the bay mares who, with Boland at the reins, will pull the glass coach carrying Lady Diana Spencer to St. Paul's Cathedral to marry Prince Charles.

Similar early morning stirrings in the London stables of the queen's household cavalry and the metropolitan police mounted division will ready the several hundred horses and riders in full ceremonial regalia who will accompany the 11 carriages. There will be three royal processions to St. Paul's from Buckingham Palace and nearby Clarence House, where Lady Diana will have spent the night with Queen Mother Elizabeth.

By the time the sun rises, tons of sand for the horses will have been spread along the two-mile procession route through the historic heart of London. The route already will be lined by hundreds of policemen, who will be joined by 2,228 officers and men of Britain's armed services.Tens of thousands of early-arriving spectators also are expected to be in place by then, many having camped out for several days.

Flags, bunting and baskets of flowers will hang along the royal mall from Buckingham Palace to Trafalgar Square and at the other end of the procession route around St. Paul's. Merchants have put up colorful decorations of their own on the rest of the route from Trafalgar Square up the Strand, Fleet Street and Ludgate Hill to the cathedral looming over the center of the city. The royal carriages will pass palaces, government buildings, Nelson's column, towering over Trafalgar Square, pubs, stores, theaters, hotels, courts and lawyers' chambers, newspaper offices and several churches designed by Christopher Wren, the architect of St. Paul's.

Police will begin monitoring closed-circuit television screens connected to outdoor cameras scanning the entire route for any sign of danger to the royal family or the several hundred other royal personages and heads of state who will traverse it later in the morning. After days of security screening at air and sea ports, many of the 4,000 policemen on duty for the wedding will check the names of every one of the thousands of persons entering buildings all along the route to watch the procession.

Technicians for 100 television companies from 50 countries will make their final tests of several hundred cameras, 750 miles of cable and 330 control circuits that will be used to broadcast the procession and wedding ceremony to more than 750 million viewers across Europe, and America and from Dubai in the Middle East to Korea and Japan in the Far East. Several thousand reporters, photographers and radio and television technicians from scores of countries, including more than 500 from the U.S., will take their places in reserved positions.

From then on, the elaborate pomp and ceremony of the world's most eagerly anticipated wedding of this half-century will be conducted with military precision afer weeks of feverish but closely coordinated preparations by a cast of thousands at an estimated cost of more than a million dollars. The queen's Lord Chamberlain has been officially in charge of the event, but Prince Charles and Lady Diana, along with the queen herself, have personally involved themselves in many details, from the wedding invitations and selection of the bridesmaids and pages, format of the wedding service and its music to the design and ingredients of the 200-pound-plus wedding cake.

With the wedding day declared a national holiday, the center of London will be reserved exclusively for the royal celebration. All traffic except public transportation will be banned. Much of the rest of the city and country are expected to fall silent as Britons watch the hours of pageantry on television before moving outside, weather permitting, for a jubilant afternoon and evening of neighborhood street parties and hotel balls.

The festivities will begin in the morning with the sound of music and bells as the crowds swell along the procession route and the first invited guests arrive at the cathedral. Bands of the queen's household guards will play on the route and the 12 big bells in the northwest tower of St. Paul's will ring in change peals for a half-hour to sound the call to the 11 a.m. service. A bank clerk, a train driver, a wholesale fruit market worker and a physician are among the cathedral's bell-ringers, who will sound the bells for another half-hour after the service and then ring a prodigious peal of changes for nearly four hours in the afternoon to celebrate the wedding.

After the doors of St. Paul's are opened at 9 a.m., the cathedral's organists will play music by English composers Arthur Bliss, Benjamin Britten, Edward Elgar, Ralph Vaughan Williams and others, as wedding guests in ceremonial uniforms, top hats and tails and fancy gowns are ushered to their seats. Built under Wren's supervision between 1675 and 1710, the massive, Renaissance-style cathedral with its familiar high dome replaced an even larger Gothic cathedral that burned to the ground in the great fire of London in 1666. During World War II, volunteer firefighters of the St. Paul's watch braved the bombs of the blitz to save the cathedral from destruction by German incendiary weapons.

There has never before been a royal wedding at St. Paul's, but the golden and diamond jubilees of Queen Victoria in 1887 and 1897, the silver jubilees of King George V in 1935 and his granddaughter Queen Elizabeth II in 1977, and the celebration service last year for the 80th birthday of Queen Mother Elizabeth have all been held there. St. Paul's was chosen for the wedding because it can seat so many people, is best-suited for the extraordinary range of music that will be performed, and provides better lines of sight for television than Westminster Abbey, where Queen Elizabeth was married in 1947. Both Prince Charles and his grandmother, the queen mother, are said to particularly like the cathedral. The queen mother is its patron, and she and cathedral officials, they said, hope the wedding will help them raise badly needed money for its maintenance. Lady Diana, according to the cathedral's dean, the Very Rev. Alan Webster, never set foot in St. Paul's until the reverend's wife took her through it in preparation for the wedding.

Both Webster and the archbishop of Canterbury, the Rt. Rev. Robert Runcie, have said they were impressed by the seriousness of the royal couple's approach to the ceremony and how much they participated in its planning. Runcie also told reporters that his discussions with Charles and Diana were not confined to the service. We talked about the reasons for matrimony," he said. "That children should be brought in the fear of the Lord, and that in a marriage one is creating a new family."

"Among those invited to the ceremony were relatives of the bride and groom, who include much of the royalty of Europe and nobility of Britain, and their personal friends, including most of Charles' old girlfriends and men who have escorted Lady Diana. One of them, a Scot named Andrew Widdowson, was crippled last year in an accident and will arrive at St. Paul's in a wheelchair. Diana also invited an American couple, New York oil company executive Patrick Robertson and his wife Mary, whose 2-year-old son Diana baby-sat as a part-time nanny when the Robertsons lived for a year in London. bShe also invited seven members of the staff of the Young England nursery school where she had worked. Charles also invited the two surviving members of his favorite group of entertainers, satirists Spike Milligan and Harry Secombe of old BBC radio "Goon Show." The third goon was the late Peter Sellers.

The queen invited the rest of the royal families of Europe, all the ambassadors accredited to the Court of St. James's, the governors-general and heads of government of the fourteen commonwealth countries (including Canada and Australia) who still recognize the queen as their sovereign, and the heads of state of the other commonwealth countries and nations of the European Economic Community and the NATO alliance.

Buckingham Palaced officials said they are still not certain about everyone who is coming, but three invited heads of state are not. President Reagan is sending his wife Nancy, the president of the Republic of Ireland declined because of a feared adverse reaction from militant Irish nationalists, and King Juan Carlos of Spain canceled because Charles and Diana will begin their Mediterranean honeymoon cruise by boarding the royal yacht Britannia at Gilbraltar, the sovereignty of which is still being strongly disputed by Spain after nearly 280 years of British rule over the rock.

After most of the congregation has been seated at 10 a.m., more prominent guests, including heads of state and members of foreign royal families, will arrive at the cathedral in motorcades. They will be followed by "junior members" of the royal family, and then by the crowned heads of Europe from Buckingham Palace, all of whom are related to the British royal family either through William of Orange, 17th-century monarch of both Britain and Holland, or Queen Victoria and her nine children. Without the king and queen of Spain, they will include the kings and queens of Belgium, the Netherlands, Denmark, Norway and Sweden, the princes and princesses of Monaco and Liechtenstein, and the grand duke and duchess of Luxembourg.

The last motorcade, coming from Clarence House, the residence of the queen mother near Buckingham Palace, will bring the bridesmaids and pages to the cathedral. The five bridesmaids are Lady Sarah Armstrong-Jones, 17, the daughter of Princess Margaret and the Earl of Snowdon, who are now divorced; India Hicks, 14, who was named India in honor of her grandfather, the late Earl Mountbatten, former viceroy and governor-general of India and Prince Charles' favorite uncle; Catherine Cameron, 6, daughter of close friends of Charles; Sarah Jane Gaselee, 10, daughter of Charles' horse-racing trainer, and Clementine Hambro, 5, who is representing the children who attended the private London nursery school where Lady Diana worked before her engagement.

The two pages are Lord Nicholas Windsor, 11, son of the duke and duchess of Kent and nephew of the queen and Prince Phillip, and Edward Van Cutsem, a godchild of Prince Charles. The bridegroom also will be attended by his younger brothers, Prince Andrew and Prince Edward.

At 10:22 a.m., the queen and other members of the royal family will leave Buckingham Palace in eight horse-drawn carriages, accompanied by mounted troops of the household calvalry, for the 20-minute ride past the cheering crowds to the cathedral.

Prince Charles will leave in another procession eight minutes later in the gold-encrusted coach normally used by the queen for ceremonial occasions. Pulled by four gray horses with their manes decorated in silver, it also will return the newly married couple to Buckingham Palace unless rainy weather forces them into a closed carriage. The coachmen and footmen for the carriages will wear scarlet and gold livery with gold-buckled shoes, white wigs and tri-corner hats with ostrich feathers.

Finally, the glass coach that has carried all British royal brides to their weddings since it was built 70 years ago will bring Lady Diana and her father, Earl Spencer, from Clarence House to St. Paul's. Following processiona into the cathedral by the queen and Prince Charles and their parties, the bride and her father will cimb along the 24 imposing granite steps to the west door of St. Paul's. It will be one of the most photogenic moments of the ceremony with the first full view of Diana's dress and trailing train.

The bride's dress will remain a secret until Wednesday morning. Designers David and Elizabeth Emanuel have been forced to make extraordinary precautions to prevent the press from discovering the design of the dress. The son of a Welch steelworker and the granddaughter of an American GI who stayed in Britain after World War II and married a British nurse, the Emanuels also are making the bridesmaids' dresses and other gowns for Lady Diana. A low-cut black dress they designed, which she wore during her first evening out with Prince Charles after the announcement of their engagement, created a sensation.

The secrecy shrouding Lady Diana's wedding dress extends even to the Lullingstone silkworm farm in Dorset in southwestern England, where the silk for the dress was spun. The farm's owner, Robert Gooden, who personally delivered the silk to the Emanuels, will not say how much of it is being used.

But the Royal Navy commander's uniform Prince Charles will wear to his wedding has frequently been seen in public for the past three years. Its design was supervised by Earl Mountbatten, who alsowas a celebrated British naval commander during World War II and later first sea lord. Representing Charles' rank in the Royal Navy, the dark blue uniform bears the insignia of a commander in three bands of gold lace on the cuffs and the royal cipher of the prince of Wales in gold on epaulettes on both shoulders. The bridegroom also will be wearing his knighthood orders of the Garter, Thistle and Bath, medals from his mother's coronation and silver jubilee, and a full dress sword tassled in gold.

The bride's entrance into St. Paul's will be announced by a fanfare from trumpeters encircling the "whispering gallery" walk around the inside of the dome high above the small platform built for the ceremony in the center of the cathedral. Their families will be seated to each side of the platform when the bride and groom stand before the archbishop of Cantebury for the wedding service already renowned by the couple's removal of the bride's promise "to obey" in making her marriage vows.

The archbishop of Canterbury has said the decision to drop this vow was made very quickly in his discussion of the service with Charles and Diana and that he told them, the usual clergyman's joke, "It's a bad thing to start your marriage off with a downright lie." He told reporters that many couples now omit this vow which he said was a remnant from the Middle Ages, when a wife would pledge "to be bonny and buxom in bed and board."

Much of the rest of the ceremony, in which the bride and groom marry each other by repeating their vows, is familiar because of the flowery language it retains from the 1928 revised version of the 1662 Book of Common Prayer of the Church of England. This remains the most popular wedding service in Britain, according to opinion polls, despite the recent widespread introduction of the new alternative service book in Anglican churches. A few of its modern prayers have been included in the royal wedding, however, in what the dean of St. Paul's has called "liturgically a compromise" of the old and new with suggestions from himself, the archbishop and Charles and Diana.

In marked and unprecedented gestures toward ecumenism suggested by the cathedral dean and Archbishop of Canterbury and welcomed by the royal couple, prayers also will be read by the Roman Catholic Archbishop of Westminster and the moderator of the Church of Scotland. Prince Charles also asked that the lesson be read by his close friend, the Rev. Harry Williams, who was chaplain of Trinity College at Cambridge University when Charles was a student there.

As the world watches on television and the crowds in the streets outside the cathedral listen to loudspeakers broadcasting the service, the groom and bride will become man and wife -- and Lady Diana will become princess of Wales -- when Charles puts the wedding ring of Welsh gold on the fourth finger on her left hand, and declares: "With this ring I thee wed; with my body I thee honor; and all my worldly goods with thee I share."

The ring is the last to be made by Garrard's, jewelers for the royal family since 1843, out of the same nugget of gold found in 1923 in the Clogan St. David's mine in northwestern Wales that was used for wedding rings for the queen mother, the queen, Princess Margaret and Princess Anne. Prince Charles, who wears a signet ring of his office on the little finger of his left hand, will not wear a wedding ring.

Later, Charles and Diana will follow the archbishop of Canterbury through the choir of the cathedral to sign the register book legalizing their marriage. Although addressed during the ceremony by the Christian names of Charles Philip Arthur George and Diana Frances, they are expected to sign the register simply as Charles and Diana. The queen and Prince Philip, and Lady Diana's parents, long ago divorced and both since remarried, also will sign the register, while soprano Kiri Te Kanawa, accompanied by the Bach Choir and musicians from three London orchestras chosen by Prince Charles, will perform an aria and chorus from Handel's "Samson."

During the service, the choirs of St. Paul's Cathedral and the queen's royal chapels will sing an anthem written for the wedding at Prince Charles' invitation by music professor William Mathias of the University of North Wales. Prince Charles met Mathias after the composer wrote a fanfare for a television program celebrating the 10th anniversary of Charles' investiture as prince of Wales. Charles retains a strong interest in Wales form his investiture, and his study of the Welsh language and culture preceding it while braving anti-British demonstrations by Welsh nationalists.

The service will end with another fanfare from the state trumpeters of the queen's household calvary, Edward Elgar's familiar "Pomp and Circumstance" and William Walton's rousing "Crown Imperial." The wedding party and royal wedding will leave the cathedral and return to Buckingham Palace in formal processions similar to those in which they arrive and enter the cathedral.

Back at Buckingham Palace, after photographs are taken of the wedding party, there will be an early afternoon "wedding breakfast" for up to 100 members of the couple's families, including related European royalty. It will feature the 4 1/2-foot-high wedding cake commissioned by Charles and Diana from the Royal Navy Cookery School in Chatham, southeast of London. Diana, personally, and expertly, according to chief petty officer David Avery, approved the cake's design and ingredients. Avery will not reveal the exact recipe, although he said it will include Navy rum at Charles' request. Although it is the official cake and the one that will be cut and eaten by the wedding party, a number of others have been accepted by the palace for display at the wedding breakfast. But recently, after being overwhelmed with offers of cakes, the palace announced that it could not accept any more, except from people "who have a particular connection with her majesty, his royal highness or the Lady Diana." Palace officials suggested that anyone who else "who wished to make a special cake in honor of the royal wedding" should donate it to a hospital or charitable home.

The cake is already finished. It took four hours to sort the currants, sultanas, raisins and cherries the cake will contain and more than eight hours to bake its biggest layer. It took tow weeks to apply and smooth layers of marzipan and icing over the cake's five tiers. Although it is the official wedding cake, there will be a number of others accepted by the palace as gifts to the royal couple.

The wedding breakfast is the third celebratory meal the queen will host at the palace during the week. Monday night, there will be a small three-course dinner for about 80 relatives and friends of Charles and Diana, followed by a reception with dancing for 1,500 people, including the royal family's large household and staff, mostly "the hoe polloi," said a palace spokesman.

On Tuesday night, the monarchs, heads of state and government leaders invited to the wedding will be among another 150 people dining with the queen. Later that night, the royal family will be driven to nearby Hyde Park for the elaborate wedding eve fireworks spectacular that will be watched by an estimated 500,000 spectators and millions of television viewers.Prince Charles also will light the first of the more than 100 bonfires that will stretch across the country through the night in a chain of beacons from the Channel Islands to Jersey celebrating the royal marriage.

After the wedding breakfast in the palace on Wednesday, the prince and princess of Wales will make the traditional appearance on the balcony of Buckingham Palace. Then they will ride in another carriage procession to Waterloos railroad station to travel in a royal train to Romsey in the Hampshire hills southwest of London to begin their honeymoon in the mansion on the Broadlands Estate of the late Earl Mountbatten, where the queen and Prince Philip also started their honeymoon. More than the usual number of tourists have been thronging to Broadlands in recent days and paying $3 to tour the house so they can search for the wedding night bed. The tabloid press has decided that it will be an imposing, covered, four-poster in the main guest room, which has pink and blue curtains on windows with a pleasant view of the estate's parkland. Britain's biggest-selling tabloid, Rupert Murdoch's Sun, devoted almost an entire page to a picture of the four-poster, under the bold-type headline: "This Is the Bed."

Two days later, they will fly to Gibraltar to board the royal yacht Britannia, which resembles a luxurious cruise liner, to sail the Mditerranean for two weeks. They are expected to stop at several Greek islands and perhaps Malta and Cyprus. The yacht will be shadowed at a distance by Royal Navy ships.

After returning to Britain, Charles and Diana are expected to join the royal family at Balmoral Castle in Scotland before settling down in the country mansion in Gloucestershire and the town apartment in Kensington Palace in London that will be their primary homes. Highgrove House, a Georgian mansion on 347 acres of farmland in Gloucestershire northwest of London, was bought by Prince Charles for about $2 million last year nad is now being redecorated and landscaped. A previous owner of Highgrove was Maurice MacMillan, son of the former prime minister. Among Charles and Diana's neighbors of Highgrove, which is located in a region of large manisons, many bigger than theirs, will be Princess Anne and Capt. Mark Phillips, who live eight miles away on the Gatcombe Park estate. Prince Charles will retain offices in Buckingham Palace.

Their 10-room apartment in Kensington Palace in the fashionable West End of London will occupy one wing of the 17th-century palace, where Princess Margaret, Prince and Princess Michael of Kent, and the duke and duchess of Gloucester also have apartments. Queen Victoria was born in the wing chosen by Charles and Diana, although the last monarch to live in the palace was King George II. Its once private royal gardens are now part of popular Hyde Park.

By the time Charle and Diana spend their first night there, the thousands of wedding presents they will have received will be on public display in St. James Palace on the mall. Those already arrriving include homemade items from loyal British subjects, a king-size bed manufactured by a firm in the west midlands, and ornate objets d'art from foreign royalty and heads of state, as well as practical items for the couple's two new households selected from wedding lists Diana established at two of London's top-of-the-market house and giftwares shops.