Old TRV Valve connection

[SK_London]

I have a tiny leak coming from the underside of the "nut" at the top of the copper feed pipe on an an old Valiant TRV valve . It probably just needs a tightening or a bit of PTFE . I understand that these are usually compression fittings but I think this might be something different as the way it is attached looks different to the more modern TRVs in the rest of the house. I don't want to start trying to force anything without understanding how this valve is attached to the copper pipe. Can anyone advise? Cheers

 

[snowhead]

It just looks like an internal compression nut instead of an external one.
There should still be a standard Olive on the pipe inside.