Nibbling on salmon, duck pate and raspberry iced souffle while two organists played "By the Time I Get to Phoenix," guests at the British Embassy, including Defense Secretary Casper Weinberger, Sen. Claiborne Pell (D-R.I.) and protocol chief Leonore Annenberg, oohed and aahed over last night's opening performance of the Royal Ballet at the Kennedy Center.

"I saw the last two acts," said Weinberger, who had earlier given a speech at the National Defense University. "I loved it."

Enthusiasm for the ballet overshadowed other topics of conversation, including the resignation yesterday of CIA deputy director Max Hugel. Weinberger's comments: "I don't know him. I never had to opportunity to meet him."

The guests strolled along the moonlit veranda and through the walled-in gardens of the embassy, sipping glasses of orange juice and wine. Others took to the cooler ballroom where photos of Prince Charles outnumbered portraits of all other royalty. Royal Ballet company members showed up dressed in everything from black tie to polka dots.

Earlier in the evening, an hour before the 8 p.m. curtain, about 20 people demonstrated outside the Kennedy Center, protesting British policy on Northern Ireland.

Victoria Dyer, a member of the corps de ballet, said, "In New York, it [the disruption of the troupe's performance there] was a bit frightening at first. But then it was a little exciting. Tonight, I just thought it was a bit stupid. There were so few of them. The princess [Margaret] didn't even show up."

If the princess had shown up for the ballet's performance, she would have heard the marchers chanting slogans such as "Brits out, peace in" and carring signs commemorating the deaths of six hunger strikers in Belfast.

"Though we have noting against the ballet itself, the Royal Ballet is a symbol of British royalty, and we are here to protest their treatment of the strikers in the hellholes of Ireland," said Mary Baggarty, chairwoman of Irish Northern Aid, one of several groups demonstrating.

One month ago, 3,000 Irish nationalists turned out to demonstrate at a Royal Ballet's performance at New York's Metropolitan Opera House with Prince Charles and Nancy Reagan in attendance. That night's performance of "Sleeping Beauty" was interrupted several times by protestors.

Although a much smaller demonstration, the issues last night were the same. Some people carried placards with British Prime Minister Margaret Thatcher's picture captioned "WANTED FOR MURDER." Other signs displayed a Christlike figure pinned, as if on a crucifix, to the Union Jack, and some demanded the boycott of British-owned companies.

James McLaughlin, spokesman for Concerned Irish Americans, displayed a four-inch-long, inch-thick plastic bullet which he claimed was made in the United States and shot at the "heads and genitals of the Irish by the Brits."

Baggarty said, "I hope the British ambassador [Nicholas Henderson] shows up tonight so we can let him know we're here."

"Eight hundred and twelve years is a terrible long time to be treated like garbage," said demonstrator Marry Ellen Kelley, who wore a T-shirt reading "Live Free or Die."