OK, this is a dumb question i'm sure, but i'm looking for tips and/or
inspiration please :-}

I have a leaky rad - it appears to be the "stub" that goes into the
rad itself, rather than the rest of the valve (which looks like this
one :

http://www.screwfix.com/app/sfd/cat/pro.jsp?id=11074&ts=60837

I haven't played much with plumbing, and although I can see how the
valve part seems to seal against the "stub" by virtue of the nuts,
which will have olives behind them (I think!), I can't see a way to
tighten the "stub" end into the rad - there are no flats I can get a
spanner on as far as I can tell to tighten it.

There's a little PTFE around the thread as it goes into the rad, but I
suspect when it was fitted, it was the plumbers' vaguely indifferent
apprentice who tightened it (or otherwise...)

I suppose i'm just a little worried that if I grab it with a pair of
pipe grips i'll just crush it (although there isn't an awful lot of
room to get a bite on it to begin with) :-}

I could even be completely wrong, and find out that the nut is
captive, and it's only the general application of PTFE to the valve
itself stops the damn thing from leaking, but I suspect not :-}

TIA :-}