Benek Chaloupka

 was a friend of the Doctor. He had been a magician but later changed his career to debunking ghost claims.

He diverted the TARDIS to Prague in 2221 to ask for the Third Doctor and Jo Grant's help. He was unable to find an explanation for the ghosts that appeared in Prague. After the Doctor solved the mystery, he explained to Jo that Benek primarily brought them to Prague for the publicity. (PROSE: Spoilsport)