A couple of 'oh dear' moments:
Back in 2003 I was having a day bashing 87's. Having arrived at Crewe I had an hour or so to kill until the next one to Lime Street, so I worked out that if the next Northbound Anglo-Scot was on time I could go to Bank Quay for a +1 onto the next one back to Crewe to fill in the time.
Problem was, i'd been up since 0400, and therefore hadn't really worked it out especially thoroughly. Having taken the 90 that produced to Bank Quay, I legged it sharpish over to the other platform to take another 90 back to Crewe, just making the +1.
Next thing I remember is the announcement passing Arpley, 'welcome to the Virgin Trains service to Euston, the next station will be Milton Keynes Central'.... Oh. My C&P isn't going to be valid there, is it....!
After an embarrassing explanation to the gripper, and an hours fester at MKC, another 90 produced northbound. I gave up and went home.
The second occasion was one Friday night. I'd gone out after work for a few, intending to get the 1919 Ribblehead home. Cleverly (or so I thought), i'd remembered to check the unit allox before I left.
1905 (plenty of time) and onto platform 5 at Leeds where the 1919 usually left from. HOWEVER - alcohol based schoolboy error - I hadn't checked the monitors.... There were a pair of 156's in, the front one of which was the unit that had been alloxed the 1919 earlier. This was slightly strange, as usually there was only one 156 in, the 1919 normally left from platform 5C, but never mind, this was the correct unit, wasn't it?
1909, and pulling out of Leeds, I was forced to conclude that no, it wasn't. A trip to Pudsey and back followed, and an hour extra onto the journey home.