- Father was a surgeon in the British Army who was stationed in the Federation of Malay when Simon was born.
- Attended boarding school in England as a chorister while the rest of his family continued to live in Asia.
- Joined the Royal Shakespeare Company after attending Guildhall School, and met Sam Mendes, who directed him as the title character in Richard III and as Ariel in The Tempest.
- Toured with the Royal National Theatre's production of Rosencrantz and Guildenstern are Dead in 1996.
- Appointed a CBE (a Commander of the Order of the British Empire) in 2003.
- Replaced Tim Curry as King Arthur in Spamalot on Broadway in 2005.