Guy's Hospital

Guy's Hospital was the facility at which Smutty Thomas worked. Becuse Charles Cranleigh believed the Fifth Doctor had been sent to Cranleigh Hall to play cricket in Thomas' stead, Cranleigh incorrectly assumed he worked with Thomas at the hospital. (TV: Black Orchid)

Behind the scenes
The script of episode one only uses the word "Guy's", but the venerated old hospital is so famous that it hardly needs the word "hospital" to identify it, as the DVD's info text makes plain.