April 19, 1984

W. APPLE Jr. LONDON, April 18 - Troops and demonstrators ringing the British Embassy in Tripoli held 25 people captive for most of today, but allowed the group to return home early this evening, the Foreign Office announced. It said it welcomed the move. In London, the police still held the Libyan Embassy under siege tonight, 36 hours after the fatal shooting of a British policewoman. Intensive negotiations with the occupants of the building produced only slight signs of progress. Under the terms of the end of the siege at the British Embassy in Tripoli, the Libyan capital, members of the group, including women and children, were allowed to return home and to move freely within the city, according to the Foreign Office.

''WE were talking in the studio, wondering where Saarinen's lost credenza could possibly be,'' said Roy Slade, director and president of the Cranbrook Academy of Art in Bloomfield Hills, Mich., ''when the custodian happened by and said there was something in the basement under a tarp. It actually turned out to be the credenza.'' For seven years Mr. Slade has been searching for the original furniture in the Saarinen house at the Cranbrook Academy as part of a larger effort to restore the house, in which the Finnish architect Eliel Saarinen and his family lived in the 1930's and 40's. Recently the architectural studio at the back of the house has received the attention of the restorers. This was the drafting room Saarinen used in his practice; it also led through a rear passage to the school's architectural atelier next door. Students and faculty members often gathered there, with the drafting tables sometimes removed for larger gatherings. ''For Saarinen, conversation and socializing were important,'' Mr. Slade said. ''There used to be tea parties in this room. There was also the famous Saarinen martini.''

Walter F. Mondale appeared to have won a decisive victory tonight in Missouri's Democratic caucuses that would add to his advantage in delegates and momentum as the campaign for the Democratic Presidential nomination goes into its second half. Mr. Mondale, at a news conference tonight in a hotel near Cincinnati, said, ''It looks like we have a solid win, a good verdict in the state of Missouri.'' ''I said earlier we had a chance of getting the delegates we need by the convention in San Francisco,'' he added. ''I believe this result pushes those chances forward some more.''

Meetings of the Green District Historic Commission usually plod on routinely enough - votes allowing a sign to be built or a house to be renovated. But Tuesday night - in the matter of the First Tax District, Block 57, Tax Lot No. 2 - the commission found itself sitting in judgment on a bit of American folklore. By evening's end, historical preservationist was challenging historical preservationist. The philosophy of how history is written was being debated. And through it all, the questions that many people here have been asking privately were being shouted: Was there really a Yankee Doodle? And if so, did he come from Norwalk?

One year ago today, shortly after midday, a lone suicide driver crashed his dynamite-filled Chevrolet pickup into the front door of the American Embassy. Seventeen Americans and 46 Lebanese were killed in that explosion. But there were other less tangible casualties as well. In retrospect, the embassy bombing, while it appeared to be an isolated incident at the time, was the beginning of a sustained and successful campaign to dislodge the United States from Lebanon.