Minutes after Thursday's announcement that Princess Di is expecting a baby in June, 1,000 Britons lined up outside Buckingham Palace to cheer her as they did when she married Prince Charles three months ago.

"It's wonderful news," said one London pensioner in the crowd. "They certainly didn't waste any time, did they?"

Royal euphoria brightened the House of Commons, which has been debating Britain's economic crisis. One member immediately made a motion to "wish the princess excellent health and suitable self-indulgence during her confinement."

An enthusiastic crowd behind barricades near the Guildhall, a ceremonial center where Prince Charles and Princess Diana were scheduled to lunch, caught a glimpse of the smiling couple.

At lunch, the father-to-be spoke affectionately of his "dear wife" and said he looked forward to telling his child about the wedding at St. Paul's Cathedral.

The 20-year-old princess' step-grandmother, prolific romantic novelist Barbara Cartland, commented: "I hope it will be a son, because it's what every English man and woman wants. In America, they seem to prefer girls."

There was an instantaneous flurry of speculation over where the baby would be born, who would design the princess' maternity clothes, what the baby would be called and whether it would be a boy, a girl or twins.

Britain's ever-ready bookmakers quickly started laying odds and taking bets. One leading bookmaker, William Hill, offered 10-11 for a boy, evens on a girl and 50-1 for twins.

Favorites to design the fashion-conscious princess' maternity clothes are David and Elizabeth Emanuel, the couple who designed her wedding dress.

Buckingham Palace said that the princess is in excellent health and will be in the experienced hands of the queen's surgeon gynecologist, Dr. George Pinker, who has already delivered seven babies for the royal family.

It was also a field day for gynecological speculation. "Twenty is an ideal age to have a baby," one top obstetrician said. "What is more, she doesn't smoke and she is from 'Social Class I,' the perfect combination."

What will the future heir to the throne, second in line after the 32-year-old Prince Charles, be called?

If it is a boy, the odds at the moment are on James (since the princess is of Stuart descent and it has been a long time since Britain had a James on the throne) closely followed by Henry (for the Tudor connection).

There is more historical leeway in the name for a girl, but there is no denying the fact that the queen and her mother are both called Elizabeth.

Whatever happens, the baby will take part of the parents' title and be known, for example, as Prince James of Wales or Princess Elizabeth of Wales.

In the village of Tetbury, Gloucestershire, where the prince and princess have set up their country home, glasses were raised in the local pub, the "Prince of Wales." Pub owner Susan Dyer said, "The regulars are thrilled to bits. The place is bubbling again -- and if the prince wants to wet the baby's head, we'll be only too pleased to see him."

Genealogists Lord Teviot and Hugh Peskett quickly researched the royal ancestry and pronounced that the baby will be 58.8 percent British and, among other things, 4.69 percent American.

Although events have moved rapidly, this is not the quickest pregnancy in royal history. In 1864, Princess Alexandra, wife of the future King Edward VII, produced a son exactly 10 months after her marriage.

With the benefit of hindsight, excited British television commentators pointed out that the couple dropped hints that babies were on their minds when they visited a maternity ward in Wales last week.

Diana asked several mothers about labor and Charles volunteered the opinion that it was a "very good thing" for fathers to be present when their children are born.

Few seem to doubt the princess will be a good mother. She has endeared herself to the British public since the day the first photographer spotted her, as a possible royal bride, surrounded by tiny tots in the London kindergarten where she taught.

Toddlers at the kindergarten were busily planning a congratulations card today, although most of them were not quite sure what it was for. "Diana loves children," headmistress Seth Smith said. "And they seem to like her very much. I think she will make a marvelous mother."

In one year, the princess has been transformed from the sweet but diffident Lady Diana Spencer, called "Shy Di" by the reporters who harried her constantly, to become the star of the royal family.

She received this accolade at the opening of a new session of Parliament yesterday when Diana, poised and serene in a sheer white chiffon gown with a tiara in her carefully styled hair, outshone the usual star, Queen Elizabeth.

The Times, normally staid and cautious, proclaimed that the princess "was shimmering from head to toe."

"She absolutely lit up the old place," one member of Parliament said. "It's hard to remember that just a year ago, she was a rather pretty, shy teen-age girl."

Last night she was the star again at the opening of an art exhibition at the Victoria and Albert Museum, wearing a frothy off-the-shoulder gown and her favorite pearl choker, now almost a trademark.

During the last three days, the princess has had late night engagements following official functions during the day but has shown no signs of flagging.

A Buckingham Palace spokesman said that the princess hoped to continue some of her public engagements but not all of them, and a planned tour of Australia, New Zealand and Canada next year now seems to be ruled out.

But she will certainly remain on center stage for the next few months as Britons, eager to forget the economic gloom and chill winter weather currently dominating conversations, now have something cheerful to talk about.