Heated towel rail turn off

[Jaykay22]

I have a combi boiler (Baxi Duo Tec)
I have two radiator towel rails one of which is in a room we don't use so would like to turn it off.
Neither of these two have thermostats, (rest of the house does.)
Any help appreciated on how to switch off one of them.

 

[exedon2]

If both valves are lockshields use pliers-grips-ajustable spanner on valve stem with care!

 

[Jaykay22]

If both valves are lockshields use pliers-grips-ajustable spanner on valve stem with care!

The right hand one cover appears to be fixed?

 

[exedon2]

You only need to turn off one valve to stop it working.
Cover probably just pulls off.

 

[Jaykay22]

So does it matter which one, can I turn off the left one in the picture?