Kilroy Was Here

"Kilroy Was Here", or "Kilroy Woz 'ere", was a commonly graffitied phrase.

Jamie McCrimmon wrote "KILROY WAS HERE" in the dust on the roof of a lift in the London Underground. When the Second Doctor asked Jamie who Kilroy was, Jamie said he was "nobody [the Doctor would] know". (PROSE: The Invasion) The phrase was also written on the wall of the near the top of the lift shaft. (TV: The Invasion)

Graffiti of a sphinx covered the "KILROY WOZ 'ERE" and "KEEP BRITAIN WHITE" graffiti on a side road off Old Compton Street in Christine Summerfield's bottle universe. (PROSE: Dead Romance)

One of the Eighth Doctor's data umphs spray‐painted "KILROY WOZ 'ERE" over Imogen's annual report. (PROSE: Seeing I)

Behind the scenes
Originally a mere background detail in The Invasion, the novelization reworked the appearance of "Kilroy Was Here" to be written by Jamie McCrimmon.