I’m removing a radiator, and the connection at one end is as shown. I’m wondering how to close the valve? As you can see the central part is not designed to be closed with a key, it’s cylindrical. The nut below the top part doesn’t seem to be turnable either.
I’m guessing this end is for the water exiting the radiator. Is it an automatic valve? I was able to close the valve at the other end no problem.
I will find out when I turn the mains water back on…
1/2" BSP cap .
or two 5pence coins on top and put the top back on
So there’s supposed to be a cap that forces down the protruding bit? The cover has been lost. I’ll ask in the ironmongers. Thanks! I switched the mains back on and all was ok but I will be fitting an end cap anyway.
It’s the thermostatic valve part that is missing. Joe is right. To turn it off the pin needs to be depressed…… (pushed in not sad!)
Probably won’t make a difference , most central heating is pressurised with a filling loop at the boiler end, the water in the radiators is never connected to the mains water
Take note of the arrow stamped on the downwards branch of the valve…
Is the answer. Screw it on the side where the radiator used to be, with some PTFE tape on the threads. You can get screw-on caps for the thermostat valve, but do check the diameter as there are different types out there depending on the age of the system (I had to get adapters when I got smart thermostats).
BSP I can spell anything wrong
That beats spelling it right and getting it wrong (like people who misjudge dyslexia) 
