Marmite

Marmite was an Earth spread. It was one of many things that did not make the First Doctor smile. (PROSE: A Big Hand for the Doctor)

Rhys Williams ate Marmite that had gone out of date. (PROSE: Trace Memory)

Behind the scenes
The production credits for DWA 264 listed each contributor with their favourite sandwich. Production editor Liza Millett's sandwich of choice was "moon cheese and marmite".