pm215 parent
I suspect that a 1970s mower for UK garden use was typically not very beefy. Wikipedia thinks Larkin had some kind of Victa.
We grew up with an '80s Victa, but it was one of the super 600 slashers with a newer 5hp engine. He probably didn't have a slasher, but the rest of their lineup used similar engines and weren't especially underpowered.
If his model was anything like ours, a hedgehog could probably crawl between the blade disc (not the blades but the thing they're attached to) and the chassis and get itself wedged in there.
Probably a reel mower. A wet fart will clog a reel mower. They were real popular back in the day.