I’m in the camp of thinking the real Paul McCartney died in 1966 in a car crash, and the person that is claiming to be Paul McCartney is really William Sheppard, or as he’s been nicknamed, “Faul”.
There was a pretty informative documentary on You Tube, which has now been removed about how William became Paul. Apparently, William won a look-a-like contest and also belonged to a musical group. I can’t remember the name of the band exactly, but I remember the last word being “Pepperettes” as the name of the group was in silver print on a blue centre of a record. The documentary showed how musically talented William was and a good song writer. Apparently, Paul McCartney wrote, played and sang “simpler” music.
The documentary also stated when Paul died, it even made the papers; however, the newspapers were told to retract the story. Who exactly told them to pull it? Not sure, but apparently, there were pictures of the story in its original print. Then documentary then discusses how William replaced Paul and eventually had many plastic surgeries to look like him. Although, William was taller than Paul and that’s one of the reasons the Beatles stopped touring because “they” thought everyone would've been able to notice the difference. It also stated that William and John Lennon didn’t get along, which is why the Beatles eventually split up.
This article by Eric Hufschmid explains how two Italian forensic pathologists initially wrote an article to disprove the theory that Paul McCartney died in a car crash, but their evidence proved otherwise. Not surprisingly, the article was quickly taken down, but Eric has saved some of what they've discovered here:
Paul is Dead: New evidence based on computer enhanced forensic techniques -7 July 2010
This gentleman here claims he’s the illegitimate son of the real Paul McCartney so if you have 90 minutes to listen to the interview, what is said in it is rather interesting:
Paul McCartney's son says Paul died in 1966
As well, this particular clip of Heather Mills is her apparently discussing the fact she found out the truth about “Faul”, and it was the reason the media vilified her the way they did.
Heather Mills - McCartneys secret 1
Anyway, this is just my opinion.