Yes, I won a prize with that bike when I still lived in Hitchin.
I was out riding not long after buying it as a project & passing through a village in deepest Hertfordshire I was waived into the village fete. There was a car & bike show, you know Vincents, Electra Glides, Velocettes - all Trailer Queens, plus the locals exotic cars, Lambos Ferraris, Aston Martin, Bristol, RR, Bentley.
I had just collected a sign a printer I knew had made & laminated for me, ready for the next Summer BSA Rally at Billing Aquadrome.
It included "the prototype twin cylinder single that was the test design for the centre cylinder of the BSA Rocket 3, launched 4 years later."
<Most Interesting Vehicle in the Show> was my prize.
Not bad for a bike costing £1,000 delivered & fixed and in use with a new MOT in just 3 days.