Briant is best known for his roles in four Hammer Films productions; Demons of the Mind, Straight on Till Morning, Captain Kronos - Vampire Hunter, and Frankenstein and the Monster from Hell.
He also appeared in television series such as Van der Valk, The Sweeney, and Jack Gold's The Naked Civil Servant with John Hurt.
During this time Briant appeared in many BBC drama series and Plays of the Month, most notably Warris Hussein's Notorious Woman opposite Rosemary Harris, George Chakiris, and Jeremy Irons.
In 1973, in Hollywood, he played the title role in Glenn Jordan's The Picture of Dorian Gray a two part Movie of the Week for America's ABC network.
Other later film and television credits include John Huston's The Mackintosh Man with Paul Newman; guest starring in Jeffrey Bloom's Veronica Clare; playing Jack Palance's son in the film Hawk the Slayer; starring in David Wolper's Murder is Easy with Olivia de Havilland; and Just Jaekin's Lady Chatterley's Lover.