With Paul's death, however, a big problem arose: the Beatles were at the peak of their career and the loss of one of their members would mean the end of the show for them and for the industry behind them. Thus, somebody had the idea of never revealing Paul's death and hiring an impostor in his place, somebody who looked like him and could play music. Some sources claimed that the imposter was an actor named William Campbell, the winner of a Paul McCartney lookalike contest and, conveniently, an orphan from Edinburgh. Of course, it didn't hurt to assume that Campbell could write the same type of songs as McCartney and just happened to have the same voice.
The arrival of an impostor in November 1966, then, could have explained why the Beatles stopped touring that same year (it would have been too easy to spot a fake McCartney performance on stage) and started to grow moustaches (the face was almost identical, but not perfect: it needed some disguise).
However, this terrible secret generated in the remaining Beatles, John Lennon, George Harrison, and Ringo Starr, a strong sense of guilt and induced them to insert many hints and clues to the truth in their songs and album covers.
