MOT time...

No it's blowing the engine fuse in the fuse box. I may have found the problem though. At some point, one of the previous owners fitted a manul switch for the rad fan, and they wired it into the ignition lead. Unfortunately, their method of connecting two wires was to expose the first wire, then wrap the switch wire around it and apply lots of insulation tape. This looks like it could have been arking, and I have now put a chocolate block connector in there, which hopefully will solve the problem. I didn't notice any chafed wires in the immediate vicinity.

Strange this is, the only thing I can see connected to the "Fuse Engine 20 amp" is the radiator fan - quite why this would stop it running is a mystery to me?!

Well, when it blows, the starter motor will crank, but no spark will occur. I had assumed therefore that the engine fuse was part of the ignition circuit, coil, spark plugs etc.

Ah, having looked at the diagram myself, I see what you mean. Perhaps the problem is somewhere else then.

Thinking about it, where is the thermostat supposed to be on mine? And is it worth attempting to make the fan thermostatically controlled again? (CB-42)