LONDON, June 14, 1982 (UPI) -- Prime Minister Margaret Thatcher, beaming after announcing a cease-fire in the Falklands Monday to a cheering Parliament, joined a crowd of noisy patriots singing ''Britannia Rules the Waves'' outside her residence.
''Great Britain is great again,'' she yelled as scores of Britons crowded around her to shake hands and celebrate.
Mrs. Thatcher, belying her Iron Lady nickname, stopped outside No. 10 Downing to chat happily with reporters and celebrants.
''It's wonderful news and it's Great Britain,'' she said, grinning. ''Marvelous forces, every single one of them.
''It has just been everyone together and this is what matters. We knew what we had to do -- and we went about it and did it.''
Then hearing a crowd of patriots singing ''Britannia Rules the Waves'' and ''God Save the Queen'' down the street, she said, ''Excuse me now, I have to go down there.''
Oblivious to security considerations, the prime minister joined the boisterous group, shaking hands with jubilant well-wishers as they sang together.
In the House of Commons, every seat was filled for Mrs. Thatcher's announcement. Cheers resounded through the chamber and members waved Parliamentary ''orders'' for the session.
The prime minister's husband, Dennis Thatcher, sat proudly in the visitors gallery.
Afterward, small crowds gathered in the chilly night air outside Parliament as the exuberant members and ministers abandoned their night's business -- a discussion on the control of atmospheric pollution in Scotland -- to celebrate.
Mrs. Rex Hunt, wife of the ousted governor of the Falklands, called it ''the happiest day of my life.''
Hunt was away at a private dinner party but she said, ''when he comes home, we will celebrate.''
Unfortunately, they had no champagne laid in, she said, ''but when we get back to the Falklands, we will celebrate with champagne. I hope that's as soon as possible.''
Some sober thoughts came, however, from parliament members.
MP David Owen, spokesman for the Social-Democrat Party, said he hoped the Argentine surrender would not be totally unconditional. ''We should leave them with a certain amount of dignity,'' he said. ''It will pay in the end.''
Tory MP Winston Churchill, grandson of the famous prime minister, called the Falklands campaign ''a momentous victory.''
''It appears that the task force has achieved all the objectives that were set. It is wounderful tribute to them,'' he said. ''Now it is a question of getting the boats to send them (the Argentines) back to where they belong.''