djkeenan

I used caution and only 3/4 clamped it with some mole grips. Did not fix.

Also tried disconnecting the Manifold Absolute Pressure (MAP) sensor and the Idle Air Control (IAC) valve to put the engine into limp mode in case one of these was the problem. No fix. I did note the quiet, high pitched whine when an MG's engine is off (key removed), comes from the IAC valve. Does your engine do this?

Dunno what to do next as I don't think it's a compression problem as engine runs fine once its going. I'm gonna have a look for oil in the combustion cylinder and double check i'm still getting a strong spark when cranking a second time.