Last Tuesday evening, my wife and I were travelling back from Reading to Carmarthen on the only train that goes from London to Carmarthen (1811 from Reading).  The Guard (can I call him that now?) told us that if we changed at Bridgend we could get to Carmarthen a lot earlier than if we stayed on the HST.

Me (being all-knowing!!!) told my wife that it was more comfortable to stay where we were and that the other train would be packed anyway.

Sure enough, at Bridgend and then again at Port Talbot we were told that by changing and catching the following train we would be back in Carmarthen about 25 minutes earlier.  So I questioned the 'guard' who told me that the train following us would not be going to either Neath or Swansea. 

Penny dropped.   It had to be either using the Llandore curve or the Swansea District Line.  It proves to be the latter and is the only train of the day that uses the route.  There is also a return working - the 0504 from Carmarthen.  Apparently the trains are used to keep drivers aware of their route-knowledge as it is a diversionary route. 

It's just a pity that it's in total darkness - maybe, in the height of Summer, it might just be light enough to see something.