Out of interest how would you know that you were doing 140 and where abouts was this?
I find it hard to believe to be honest-generally speeding is taken very seriously and is something that drivers do not do as it's not worth loosing your job over. With downloads, un-announced back cab rides, ray gun checks etc I can't see why a driver would do that? Plus doing 140 on a 125 line is enough of a difference for the signal box to notice. You would be clearing sections far too quickly!
I used GPS onboard. I know we've had many theads that argue GPS isn't accurate, but I beg to differ. The train doesn't happily run at speeds of up to 125mph for the bulk of the journey and then suddenly jump to 139/140mph for some miles, before going back to around 125mph.
It was north of Peterborough, but it was also at night and I cannot remember exactly where I was. My smartphone (yes, back in 2003!) had a map but didn't log the route for later analysis, which is annoying as I'd have been able to show exactly where it speeded up and slowed down.
I have no idea if a driver felt it was worth risking his/her job, or indeed if anything did happen (not that I reported it, but if there's any data logging then who knows if it was subsequently discovered?). I can't speak for their actions.
We'd left Edinburgh and not long after leaving, something happened that delayed us (from memory) about an hour. We were then very late on our approach back to London, which was late Sunday night.
We recovered a fair bit of time, presumably as the line was fairly clear of traffic and allowed for it to try and catch up. We slowed once we got beyond Peterborough (towards London) and I remember us overtaking a FCC service because it was the service we needed to get in order to get back to Hatfield (changing at Stevenage). I can't quite remember but think it was the last London-bound FCC service that night.
Assuming my GPS didn't have some weird and unexplained fit, I can't believe it was a totally isolated one-off incident. This was 9 years ago, but I am sure someone who worked for GNER at the time would know if this ever happened more than once with disruption at night, when the circumstances might have allowed for a clear run at a higher speed - legal or not.
It's fair to say that for there to be so many ways to check speeds, there are drivers that must be speeding - or else there would be no need to check!