Robert St Clair Grant was an English actor, comedian and writer, best known for playing bus conductor Jack Harper in the television sitcom On the Buses, as well as its film spin-offs and stage version.

On the Buses is a British television sitcom that was broadcast on ITV from 1969 to 1973. It was created by Ronald Chesney and Ronald Wolfe, who wrote most of the episodes. It spawned three spin-off feature films and a stage version. Despite the writers' previous successes with The Rag Trade and Meet the Wife with the BBC, the corporation rejected On the Buses, not seeing much comedy potential in a bus depot as a setting. The comedy partnership turned to Frank Muir, Head of Entertainment at London Weekend Television (LWT), who loved the idea; the show was accepted, and despite a poor critical reception became a hit with viewers.