"Marratxi" wrote in message
...

Yes, I can see that but I've also travelled in from Watford Junction on
the
DC lines and I can tell you that there seems to be quite a long layover
there with as many as two or three trains in the station.

One is often stabled there as cover in the event of a failure. You could
argue that this should be used in the event of serious late running but the
problem is most likely then one of late incoming train crew.