The BBC features Paul talking about the event here.
And here's Paul talking to Esquire in 2015 about his first Lennon encounters:
I mean, I know how I saw John. He was just a ted, on the bus – greasy hair, long sideburns, shuffling around like he was Mr Hard. And I saw him on the top deck of the bus often, before I met him. Saw him in the queue at a chip shop once. And I thought, "He looks cool."