Any idea what TV show this was?

[AndyClockwise]

I've been trying to remember the name of a TV series from a few years ago and I hope someone can help.

I think it was about 9 years ago and I'm sure it was on BBC1.

A man gets hit by a train (suicide?) his wife subsequently discovered a flat that neither she not his friends knew about.

[AndyClockwise]

Halb said:

What happens in the flat?

I think he was having an affair

[AndyClockwise]

chilistrucker said:

I have no idea why, but the first thing that entered my head was, "Luther."
God knows why?

It definitely wasn't Luther, this was one series only that was quite short (4 episodes?)