Christopher Ellison(I)

When he first appeared in The Bill (a guest role in episode 1) his character was called Tommy Burnside, but by the time he emerged as a regular character he had become Frank Burnside! This was because, by the time he joined the series as a regular, a real police officer named Tommy Burnside was serving in the Metropolitan Police and as a result, the producers of The Bill had to change the character's name.