Draining (domestic) radiator

[RetroPug]

Hi,

Probably a really easy answer that I'm just missing but in the interest of saving myself some time, which is often quite limited, I'd like some advice on radiator draining as I'm sure someone on here will know.

I'm trying to stop water flowing into the radiator to then remove it from the wall for decorating purposes. One end looks like a lockshield valve which I have turned clockwise all the way, then on the other end there is a thermostatic valve, when removing the head after switching it to the off position it looks like the attached picture.

The issue is, after having done this, I am undoing the pipe fitting to the radiator between the thermostatic valve and the radiator and the water just keeps coming, and when the central heating is on this water is warm (radiator is cold and always off as I currently do not use the room) which suggests it is coming from the rest of the system and not the radiator.

The valve doesn't seem to tighten further with just a spanner (unless I need more force but I'm wary of breaking it). Does anyone know how to shut off this type of valve?

Thanks