He is known for television roles including Hogarth in Big Breadwinner Hog (1969), the future King George IV in Prince Regent (1979); smooth neighbour Paul Ryman in the sitcom Ever Decreasing Circles (1984–89); and Hugh "Shrimpie" MacClare, Marquess of Flintshire, in Downton Abbey (2012–15).
Egan's other roles have included the character Michael Cochrane in the programme The Ambassador (1998), and (on film) as the suave secret agent Meres in television spin-off Callan (1974), and the Duke of Sutherland in Chariots of Fire (1981).
In 2012, Egan first appeared as Hugh "Shrimpie" MacClare, Marquess of Flintshire, in the Christmas special episode of ITV's Downton Abbey.
Later that same year, Egan appeared in Alan Bennett's People, alongside Frances de la Tour, at the National Theatre.
Also in 2012, Egan narrated a new recording of Rick Wakeman's album, Journey to the Centre of the Earth, based on the story by Jules Verne.
[14] Three months later, Egan was announced as patron of the science-based campaign For Life On Earth (FLOE), which fights against animal testing in the field of human medical research.
[16] In 2018 Peter Egan joined Animal Equality UK inside a foie gras farm in France to document the process of force-feeding.