Name the TV Movie - about 5/10 years ago?

I watched a TV Movie about 5-10 years ago and I'm pretty sure it was
on the BBC, pretty certain it wouldn't have been in the cinemas as it
felt like a BBC self production. Basically (I think) there are 2 men
who are business partners, and the wife (attractive blonde) of one of
the men discovers that her husbands business partner has a heart
problem, and should avoid certain things - one of which being sex. If
he dies then her husband gets the whole business.

The male actor is vaguely famous, maybe late 40s/50s at the time, I
can picture his face but I have no idea of a name (Possibly Warren
Clarke, or someone who looks like him, and yes I've looked through his
IMBD). At one point the blonde lady dresses up as a tennis player, and
later they have sex in a corn field. This film has been bugging me for
the last few days/weeks as someone mentioned it to me, and I know what
they mean but cannot find out what it is!

HELP!