Barrett began his career as a child actor, appearing on BBC children's television and in films such as Bang!
[1] Years later he made many appearances in television and films including ITV Television Playhouse, Z-Cars, The Wednesday Play, Cast a Giant Shadow, Emergency Ward 10, Chronicle, Armchair Theatre, Hell Boats, Moonstrike, Attack on the Iron Coast, Softly, Softly, BBC Play of the Month, Paul of Tarsus, Tales of the Unexpected, Father Ted, Holby City, Brush Strokes, Minder, Poldark, Noah's Ark and Theatre 625.
He has performed the voices of Asterix, Caius Tiddlius, Fulliautomatix, Roman Ghost, Cylindric, Mannikinpix, Gladiator Trainer and Jailer in the English version of The Twelve Tasks of Asterix, Tik-Tok in Return to Oz, a Goblin in Labyrinth, Big Mac and other characters in TUGS, Thadius Vent's soothsayer Goodtooth in Oscar's Orchestra, Melchoir in the English dubbed version of the Lapitch the Little Shoemaker TV series, Roly the Pineapple in the English version of The Fruities and UrSu the Dying Master and UrZah the Ritual-Guardian in The Dark Crystal as well as additional characters in two video games The Feeble Files and Viking: Battle for Asgard.
He also provided the voice for Captain Orion in Star Fleet, the English version of the 1980s Japanese puppet series X-Bomber.
In 1985, the rock band The Smiths used a still of Barrett as a teenager in the 1958 film Dunkirk for the sleeve of their hit single How Soon Is Now?