In the 1980s the CS [or at least the Met. Office MoD part of it] got knickers twisted with travel rules, as also did Rail with its pricing strategy.
I slaved under rules that demanded the smallest total outlay for, say, a day duty in London when based in Leeds. I hope memory serves correctly, but these days there are risks attached.
My very switched - on gopher did the homework and frequently bought me the following:
Car parking at Doncaster Station [living in Gainsboro, commuting daily to Leeds]
White Rose Pullman Doncaster to KX First Class, and return
Full English, plus newspaper
and Half day subsistence for lunch in town, usually liquid, with the balance paying for dinner on the train on the way north.
TOTAL LESS THAN CATTLE CLASS PLUS FULL DAY SUBSISTENCE.
Needless to say I rather looked forward to a summons to the Smoke.
Mad, my masters, mad