When planning a visit, it is often wise to check that your host will be in. It might be imagined that such niceties of etiquette would apply particularly when popping in on the Prime Minister – but not if you are Mikhail Gorbachev.
In December 1984 the future Soviet leader turned up unannounced in Downing Street, only to find that Margaret Thatcher was attending to business elsewhere, according to government papers.
Mr Gorbachev’s diplomatic over-familiarity may have arisen from his talks with Thatcher a few days earlier, after which she famously described him as a man she could “do business with”.
More freshly released information from the National archives: