Complex sentence: In 1981 Thatcher and François Mitterrand, the French president, agreed to set up a working group to look into a privately funded project, and in June 1982 the Franco-British study group favoured a twin tunnel to take conventional trains and a vehicle shuttle service.
Split into simpler sentences: In 1981 Thatcher and François Mitterrand, the French president, agreed to establish a working group to evaluate a privately funded project. In June 1982 the Franco-British study group favoured a twin tunnel to accomodate conventional trains and a vehicle shuttle service.