In ceremonies rich in regal grandeur and full of military honor, Britain bade farewell today to assassinated Lord Louis Mountbatten, heroic World War II naval commander, the last viceroy of India and elder statesman of the royal family.

Tens of thousands of people lined the cortege route and millions more watched on television as officers and men from the military services of six nations accompanied Mountbatten's flag-draped coffin in a mile-long procession from St. James's Palace to Westminster Abbey for a funeral service attended by royalty and government leaders from throughout the world. Mountbatten's body was then taken 90 miles to the green Hampshire hills, where it was buried under the flagstone floor of Romsey Abbey, his parish Anglican church.

It was the most solemn state occasion here since the death of Winston Churchill in 1965. The nation's grief was heightened by the manner of Mountbatten's death nine days ago, when an Irish Republican Army terrorist bomb blew apart his fishing boat off the northwestern coast of Ireland near the border with Ulster. The security for today's funeral was the tightest in memory here.

"He was a father figure to Britain," said London lawyer Robert Smith, as he watched the procession. "There won't be another like him."

"Killing him was a sick thing," added Dorothy Bailey, a secretary in the Ministry of Defense. "We identified with Mountbatten. He was an aristocrat, but we could understand him. I don't know if he's the last of his kind in Britain. I hope not. We need men like him now."

The bomb that killed Mountbatten and three others on his boat was the first blow struck against the royal family by the IRA during its long terrorist campaign to drive the British out of Ulster and unite it with the Republic of Ireland to the south.

The queen, dressed in black, and Prince Philip and Prince Charles, both in full dress naval officer's uniform, could not hide the personal grief evident in their anguished faces.

At his death at age 79 he was Earl Mountbatten of Burma, admiral of the fleet and aide-de-camp and monarch's protector to Queen Elizabeth II. A great grandson of Queen Victoria, he was a second cousin of Queen Elizabeth and an uncle of her husband, Prince Philip.

Mourners at Westminster Abbey included Queen Elizabeth and her family, King Olav of Norway, King Carl Gustaf and Queen Silvia of Sweden, Prince Georg of Denmark, Princess Beatrix and Prince Claus of the Netherlands, Prince Albert of Belgium, Prince Ranier and Princess Grace of Monaco, and the Grand Duke Jean and Duchess Josephine-Charlotte of Luxembourg. It was the largest gathering of royalty since the funeral of king George VI in 1952.

Prime Ministers Margaret Thatcher of Britain and Jack Lynch of Ireland were among government and military leaders at the funeral. Averell Harriman, a wartime ambassador to Britain, represented President Carter. Officers and men from the military services of the United States, Canada, France, India and Burma -- those Mountbatten was closest to during and after the war -- had roles of honor.

Many of the arrangements for his funeral were made by Mountbatten several years ago. "Dying doesn't worry me," he said just last month in a BBC television interview. "I'm looking forward to my own funeral. It should be a great do and great fun."

The procession began in bright sunshine on a cool morning at St. James's Palace, halfway along The Mall between Buckingham Palace and Trafalgar Square, where Mountbatten's body had lain in state overnight.

His coffin, covered by the Union Jack, was put onto the cortege gun carriage by the Royal Navy pallbearers that Mountbatten had specified. On top of the flag were placed his admiral's cocked hat, a ceremonial sword and the gold stick that was his symbol of office as the monarch's protector.

The gun carriage was pulled along by 131 Royal Navy sailors and officers as the commanding officers of Britain's armed services walked beside it. They were preceded down the Mall, which was lined with soldiers in ceremonial red coats and tall black fur hats, by royal bands playing slow marches accompanied by a steady funeral drumbeat.

Behind the bands were six officers from British, Burmese and Indian military services, each carrying a pillow bearing some of the most important of Mountbatten's insignia and honors from 10 nations, including the British Order of the Garter, the Order of the Star of India, the French Legion of Honor and the Order of Merit of the American Legion. Mountbatten was most honored for his victorious service against the Japanese in Burma as supreme allied commander in Southwest Asia and for his postwar supervision of Britain's granting of independence to India.

Just ahead of the gun carriage carrying Mountbatten's coffin walked a black riderless horse, the 22-year-old charger Dolly that Mountbatten rode along part of this same route during the annual trooping of the color ceremony celebrating the queen's birthday. His boots were set in the stirrups backwards.

Behind the coffin walked members of Mountbatten's family, and Prince Philip and Prince Charles, both favorites of Mountbatten. He helped supervise Philip's upbringing and encouraged his marriage to the future Queen Elizabeth and he was an adviser to Prince Charles in his preparation for eventually succeeding his mother on the throne.

Following them were representative groups of veterans who served under Mountbatten in World War II, including a contingent of those who served on the destroyer HMS Kelly and survived with him when it sank off Crete early in the war.

Passing the statue on the Mall of George VI, confidant of Mountbatten, the procession turned to pass through Horse Guards Parade -- the arch familiar to tourists for the changing of the guard ceremonies there. Onto Whitehall, the government avenue of London, the procession passed Downing Street and the Parliament building, before stopping at the great west door of Westminster Abbey.

Inside Westminster Abbey, Britain's religious leaders participated in the service of hymns selected by Mountbatten. The lesson, part of Psalm 107, "They that go down to the sea in ships," was read by a uniformed Prince Charles.

Bugles played The Last Post and the abbey organ played Handel's Death March. Mountbatten's coffin was then taken by an Army Land Rover to Waterloo Station and put on a special train that carried it and the royal family to Romsey.

In the 12th century abbey there Mountbatten was buried under the floor of the south transept. His body was placed in an unusual north-to-south position so that he will be facing the sea.

"My only wish as a boy," Mountbatten told the BBC in the broadcast interview which according to his wishes was televised as part of the funeral broadcast today -- "was to enter the Royal Navy and serve there for the rest of my life. I'm extremely proud just to have served in the Royal Navy."