Granada TV's World in Action team were at Christ's College, Finchley, on Friday, to record a lecture given by Mrs Thatcher to students of the economic sixth form.
She was introduced to the students, who are studying British government, by Mr David Howes, Master of Economics.
Mrs Thatcher described how Parliament works and the time spent before a Bill becomes law. To illustrate the volume of paperwork used in one day's sitting of the House, she took along a big bundle of publications, including a copy of Hansard, which records every word spoken during a session.
Mr Howes thanked Mrs Thatcher for her insight into her work as an MP, then invited the students to ask her questions.
And she spent nearly 30 minutes answering queries, ranging from the forthcoming Common Market referendum to electoral reform.