"Nunquam Dormio"

Was the motto of 605 Sqn, one that flew Whitley Bombers at some stage.  I didn't, I'm sorry to write, work out the model of motorbike, but it made quite a sight, parked on the pavement (I normally grumble about pavement parking :-() on the corner of the street in Hitchin today.

Does anyone recognise the model (of motorbike)?