Pretty much as per the subject - when did London Transport start
offering free travel overnight on 31 Dec/ 1 Jan? And has it always been
the same 23.45 to 04.30 time window?

Also, remind me - I'm pretty sure the all-night Tube services on NYE
came about because of the Millennium celebrations of '99 into 2000 - but
have they run every single year since?

I recall there was a lot of disappointment when the NYE 2000 into 2001
London firework celebrations that had been planned didn't in the end go
ahead (2000 was the first year of the Mayorlty under Ken), but I *think*
they've happened every NYE since 01/02 in one form or another.

No Christmas travel info on the TfL website yet. I think they should at
least have a basic outline up by the beginning of December - people
aren't born with the knowledge there's no service on Christmas Day, or
that whilst almost all mainline rail services aren't running on Boxing
Day the Tube is.