Malcolm Smith - 1964 Greeves 360 Griffon 

Richard "Fiasco" Johnson would approve!

The Greeves Challenger was a 250 or 360. The Grffon was 380cc .the bike shown is a later Qub 380. Bert Greeves made invalids cars which used Villiers engines

Sounds like you possibly were riding a 1964 Greeves Challenger. The Griffon wasn't made in 1964. 1964 was when the Challenger came out.