The Profumo Affair was a 1963 British political scandal named after John Profumo, Secretary or State for War. Profumo had an affair with Christine Keeler (pictured above), who was also reputed to have been involved with a Russian spy.
Not only was Profumo married but Keeler was a "London call girl" (a quaint term of the time). And an affair that close to a Russian spy was surely bad form in the middle of the Cold War.
Revelation of the whole sordid entanglement was, as one would imagine, devastating, as was the fact that Profumo lied about it in the House of Commons when questioned.
He was forced to resign, which badly damaged the reputation of Prime Minister Harold Macmillian's government. Macmillan himself resigned a few months later due to ill health.