Well, according to the Norton enthusiast on the Norton Owners Club stand at Wimbotsham bike show on Bank Holiday Monday, not a lot. Forty-five miles an hour, flat out, downhill with a following wind.
But there aren't any hills in Fenland, don't be picky about trivia, there's so much torque you won't even have to change gear once you're moving...
Apparently the bike was owned, pre-war, by a saddler in Downham Market who used the flat-bed sidecar just like a pick-up to deliver his wares and was a common sight in the area.
The boss says no, so I'm retiring to the shed to do a bit of fettling.
I'd rather have a Royal Enfield anyway.