Tom Anderson wrote:

It doesn't address the problem with recharging your oyster at night,
though. I would have thought that could be done fairly simply by having
some oyster machines - which could be of the card-only type - on the
outside of tube stations, and so accessible outside opening hours.

Great for the tube areas but what about those parts of London where the tube
is not within walking distance? Virtually all the shops that charge Oysters
that I know of close at least two hours before the tube does.