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)

During the Shoreditch Incident, Ace spray-painted "Ace woz 'ere in 63" on the bulkhead of the shuttle of the Imperial Daleks. (PROSE: Remembrance of the Daleks) In 1940, Ace was held prisoner by the Nazis in Le Mur Engineering on Jersey. When considering the possibility that she would be killed, she wanted to add her final message to a memorial wall, but though "Ace woz 'ere" would have been inappropriate. (PROSE: Illegal Alien)

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.