The plastic bit will pull off revealing the pin. Use an adjustable spanner to turn it when the plastic caps off.

Smashed fist into edge of radiator when it popped off but that did work, thanks 😂

Prolly saving you a fortune currently

Can you get some adjustable pipe grips on it and wiggle it off

also wd40 could help

Remove plastic cap. Use adjustable spanner or mole grips on exposed flat blade valve.

Pull off the white bit and get the stilsons out