Last week’s “oddity” mentioned the Krays, London’s notorious gangster twins. And Ronnie and Reggie hold an interesting unique achievement … They are the only people to have been both imprisoned in the Tower of London and to have performed at the Royal Albert Hall.

In 1951, the pair fought in a boxing tournament at the Royal Albert Hall. The following year they were locked up overnight at the Tower for being absent without leave during their compulsory National Service.
Gleaned from The Londonist at http://londonist.com/2014/07/five-more-odd-facts-about-london.php