After Paul faked his own death, and William Campbell took over, Paul retreated to his city lair in St John's Wood.
There he stayed brooding about the love of his life: Yoko. In 1973, he got up enough courage to press his suit, and he and Yoko fell in love. John did not know about this affair, so was a sitting duck for a "reconciliation", and the start of the plot on his life. Paul pulled the trigger that night, but Chapman had been handsomely paid off to take the rap.
Paul now lives as a recluse in the Dakota with Yoko. For those of us in the know, he has been writing classic songs for over 30 years now, and the world cannot hear them. His hell is that William Campbell continues to pump out rubbish in the Macca name. But his love for Yoko is strong, and he will not blow the whistle.
Any objective evidience? Not a whit, but does that matter?