I've just fitted a 35HE and that yellow bit is tight, I ended up
ripping it off with a pair of grips.

I could try mole grips. However, the thing is mostly buried, so I'm not sure
what purchase I can get on it.

Luckily the knob is fairly sturdy, a good tug was required.

Whilst the knob itself looks sturdy, I'm not sure about the control it is
attached to. It moves too much for my comfort.

Christian.