He has also appeared on numerous shows such as Midsomer Murders, Rome, Angels in America, Doctor Who, Galavant, Hawkeye, and The Witcher.

[3] Callow was a student at the London Oratory School in West Brompton,[4] and then went on to study briefly at Queen's University Belfast in Northern Ireland,[5] where he was active in the gay liberation movement.

In the early 1970s, he joined the Gay Sweatshop theatre company and performed in Martin Sherman's critically acclaimed Passing By.

[7][8] In 1977, he took various parts in the Joint Stock Theatre Company's production of Epsom Downs and in 1979, he starred in Snoo Wilson's The Soul of the White Ant at the Soho Poly.

[9] Callow appeared as Verlaine in Total Eclipse (1982), Lord Foppington in The Relapse (1983) and the title role in Faust (1988) at the Lyric Hammersmith, where he also directed The Infernal Machine (with Dame Maggie Smith) in 1986.

[10] He played Mozart in the premiere of Peter Shaffer's Amadeus at the National Theatre (1979), also appearing in the 1983 BBC original cast radio production.

[10] Callow appeared with Saeed Jaffrey in the 1994 British television drama series Little Napoleons, playing a scheming Conservative councillor in local government.

He has starred as Count Fosco, the villain of Wilkie Collins's novel The Woman in White, in film (1997) and on stage (2005, in the Andrew Lloyd Webber musical in the West End).

Chops" by Charles Dickens, adapted and directed by Patrick Garland; repeating them from December 2009 to January 2010 at the Riverside Studios and on tour in 2011.

Between March and August 2009, he played Pozzo in Sean Mathias's production of Waiting for Godot by Samuel Beckett with Ian McKellen as Estragon, Patrick Stewart as Vladimir, and Ronald Pickup as Lucky.

[19] Callow portrayed Pliny the Elder in CBBC's 2007 children's drama series, Roman Mysteries in the episode "The Secrets of Vesuvius".

In 1992, he directed the play Shades by Sharman MacDonald and the musical My Fair Lady, featuring costumes designed by Jasper Conran.

[21] In 1995, he directed a stage version of the classic French film Les Enfants du Paradis for the Royal Shakespeare Company.

[25] One of Callow's best-known books is Love Is Where It Falls, an analysis of his 11-year relationship with Peggy Ramsay (1908–91), a prominent British theatrical agent from the 1960s to the 1980s.

In November 2007, he threatened to resign the post over controversy surrounding the Terrence Higgins Trust (an AIDS charity of which Callow is also a patron).

Callow is the reader of the audio book edition of William E. Wallace's Michelangelo, God's Architect, published by Princeton University Press.

[28] Callow played Stroganoff in the 1987 Saturday Night Theatre production of A Bullet in the Ballet dramatised by Pat Hooker on BBC Radio 4.

In an interview, Callow stated: I'm not really an activist, although I am aware that there are some political acts one can do that actually make a difference and I think my coming out as a gay man was probably one of the most valuable things I've done in my life.

[34] In August 2014, Callow was one of 200 public figures who were signatories to a letter to The Guardian expressing their hope that Scotland would vote to remain part of the United Kingdom in the referendum on that issue.