How can I turn down this traditional towel radiator with tap valves?

[adam861]

I have recently had this radiator fitted and currently it gets very hot. I would like to turn the radiator temperature down however I'm unsure which valve I need to turn. I am not sure which is the flow or return. Or does it not make a difference?

At the moment, both valves in the picture are fully open.

For any comments regarding balancing... this is the only radiator in the house that doesn't have a TRV. I have a mix of Drayton Wiser smart TRVs and regular 'dumb' TRVs.

 

[adam861]

I forgot to add above another option, would it be better to reduce my boiler flow temp instead, as this is the only rad on my system that is not controlled by a TRV?