I was doing some browsing due to procrastination and found a VERY early morning train: the 1B39 03:03 Carmarthern to Swansea. I'm assuming that there are no other Arriva Trains Wales services that run this early. I mean, there could be so don't take it for granted.
That got me wondering: what is the earliest that other TOCs run trains?
Also, what would the passenger flow be like on that service?
Those early morning services in West Wales are often contenders. There's quite a range of silly o'clock stuff in that part of the world, from time to time with no obvious ferry or London connections either.
Can of worms there.
Some run throughout the night (e.g. Gatwick Express, except this winter due to engineering work).
The sleeper portions which split off in Scotland are also service trains, so they are pretty early.
Most I would imagine start around the 05:00 mark.
Gatwick Express hasn't run anything close to an overnight service for some time, and the extended "engineering works" (largely non-existent) related reductions have been in place since early summer.
I believe there are Transpennine airport runs much more extreme than anything in the current GX timetable.
You've got a very good point about the Sleepers though, I'll give you that!
It depends what you class as early.
Im sure from stations like Waterloo or Victoria there will be departures at 000x, which is technically the very start of the day.
From a ticket point of view, I believe your ticket is valid up until 0500 the day after the date on the ticket. So the earliest train would be the 050x from a station.
0429hrs. 0500 is after the start of service on many routes, and there could, I suppose, be some where day tickets valid until 0500 might undercut open ones.
First Brighton Main Line service is 0405 from Blackfriars, or 0415 from Brighton with Thameslink Mon - Fri, but weekends Southern kicks off at 0350 from Brighton and 0400 London Vic.
Now, here's a question, does a new railway day start at 0000 or 0431?
Southern runs at least hourly between Victoria and Three Bridges on Fri->Sat and Sat->Sun nights. No first or last trains on that bit.