Radio history: Margaret Thatcher faces the world in BBC phone-in

When Anna Wee dialed the phone in her Hong Kong home one day in October, she was soon talking not to a neighbor, but to British Prime Minister Margaret Thatcher 6,000 miles away - and to a radio audience of up to 100 million.

The afternoon marked a turning point in the history of the radio phone-in, once a low-key, local affair that radio executives considered little more than a cheap way to fill air time. Behind this coup was the World Service of the British Broadcasting Corporation. At 51, this oldest and most respected of international broadcasting operations had cast aside a somewhat fusty image to score another first.

Mrs. Thatcher was the first prime minister ever to take part in a global phone-in.

Anna Wee and the dozen or so other callers who spoke to Mrs. Thatcher were fortunate to get through: For an hour and a half before the 60-minute program went on the air, all lines to the London studio where Mrs. Thatcher sat were jammed with calls from every continent except Antarctica.

The prime minister's decision to participate in the phone-in was ''most courageous,'' according to the program's producer, Elisabeth Smith. ''She accepted with no holds barred. We couldn't brief her because we didn't know what questions would be coming in. All she knew was that the program would go out live and that we planned to discuss major issues of substance.''

As it happened, the day Mrs. Thatcher spoke to the world fell on the weekend after the United States intervention in Grenada. A caller from neighboring Barbados asked her why, with her known opposition to communism, she had failed to act decisively there. Her reply - making plain the depth of her anger at the American action - made the headlines of every British newspaper the next day.

Anna Wee's question - how Mrs. Thatcher reconciled her role as wife and mother with her responsibilities as prime minister - also prompted fresh revelations, though of a less newsworthy kind. Explaining that her children were grown up by the time she became prime minister, Mrs. Thatcher said: ''I've been most fortunate in the way things have bounced for me all my life.''

She disclosed that there was no cook at 10 Downing Street, and that she tended to prepare the evening meal for herself and her husband, Dennis. Mrs. Thatcher said she ''rather enjoyed'' housework.

When the world phone-in project was proposed, even experienced broadcasters trembled in their crepe-soled shoes. Elisabeth Smith says: ''When we embarked on the phone-ins, we hadn't a clue as to whether they would work. In this kind of program, there's always an element of the unexpected.''