He has appeared in a variety of roles in film, television, stage and radio, often playing comic characters. He is best known for his role as Lord Ashfordly in the Independent Television Drama Heartbeat and for playing Lord Yohn Royce in the Home Box Office series Game of Thrones in season 4 and season 5. Vansittart is known to fans of the 1995 Pride and Prejudice serial as the actor who portrayed Mr Hurst, the brother-in-law of Charles and Caroline Bingley.
He has also worked with Rowan Atkinson on a number of occasions, appearing as a guest star in two episodes of Mr.
Bean and also The Thin Blue Lincolnshire, as well as appearing in Johnny English Reborn, the sequel to Johnny English. Vansittart was one of three surviving cast members from the original 1992 series of Heartbeat, having had a frequently recurring role as aristocrat Charles, Lord Ashfordly.
In 1993, he appeared in Remains of the Day as Sir Geoffrey Wren, a character based on the 1930s British fascist Sir Oswald Mosley. In 1994, he appeared in the film Braveheart as Lord Bottoms.
He worked in Four Weddings and a Funeral as George the Bore at the Boatman in 1995.
In 2003, he appeared in the West End adaptation of Arsenic and Old Lace. In 2005, he appeared in the "Market for Murder" episode of Midsomer Murders and, that same year, as General Asquith in the two Doctor Who episodes, "Aliens of London" and "World War Three". In 2006, Vansittart portrayed Thomas J. Dodd in the British Broadcasting Corporation three part drama documentary Nuremberg: Nazis on Trial.
He also appeared in the 2008 British Broadcasting Corporation serial Spartacus as Consul Lentulus, and in 2009 in Margaret as Peter Morrison.
In 2009 was his second appearance in "Midsomer Murders", episode was titled "The Dogleg Murders". He played Harrison Ashton Lard, the "posh girl"s father", in How Not to Live Your Life.
He provided additional voice-over for World"s Craziest Fools. He appeared in the final two seasons of Foyle"s War as Sir Alec Myerson, the title character"s boss at MI5.
Vansittart also appeared in the British Broadcasting Corporation Three comedy Bad Education, playing Mr.
Humpage. In 2016 he appears in the British Broadcasting Corporation television series Father Brown as Arthur Le Broc in episode 4.7 "The Missing Manitoba". In January 2016, he played character Peter Jennings on an episode of the British Broadcasting Corporation series Casualty.