WHO 1

WHO 1 was Bessie's original number plate. (TV: Doctor Who and the Silurians)

It was later changed to WHO 7 (TV: Battlefield) and then, further, to WHO 8. (PROSE: The Dying Days)

The yellow roadster's plate again read WHO 1 after the Eleventh Doctor transformed it into a monster truck. (COMIC: What He Wants...)

Behind the scenes
The WHO 1 number plate was already registered elsewhere, so special WHO 1 plates were made and used on the car when filming on private ground, and on the public highway with permission from the police. Bessie's real-life registration was MTR 5.