He appeared as Paroli in the 1984 Doctor Who serial Warriors of the Deep and provided the voice of the Krargs in the lost episode Shada, written by Douglas Adams.
He has appeared in many films including Murder with Mirrors co-starring with Bette Davis and Helen Hayes, and played Richard Gere's son, Amnon, in the Bible epic, King David.
Coombes has worked extensively in the theatre including seasons at Chichester Festival, Pitlochry Festival, Bristol Old Vic, London Young Vic, The Arts Theatre, London, Ludlow Festival, Coventry, Southampton Nuffield and Birmingham Rep. Other credits include: Minder on the Orient Express, The Country Diary of an Edwardian Lady, Capital City, US mini series Napoleon and Josephine, Boon, The Kenny Everett Television Show, Drop the Dead Donkey, Saracen, Heartbeat, Bugs, Holby City, Starhunter, The Bill, My Family and Dinosapien.
He appeared as Paul Deroulard in "The Chocolate Box" episode of Agatha Christie's Poirot, and was Gennaro Lucca in the Jeremy Brett Memoirs of Sherlock Holmes adventure, "The Red Circle" .
As well as acting, Coombes regularly tutors at the Academy of Creative Training in Brighton and guest directs at ArtsEd School of Musical Theatre, and Drama Studio London.