Peter Frimberley ) gurgled happily,
sounding much like they were saying :

You can share a prepay Oyster card with other people but not during
the same journey.

And the system should have some assumption built in about the minimum
duration of a bus journey, but you you don't touch off a bus, so there
is no definite time when you stop using it (and can pass it to someone
else).

We don't know that it doesn't have such an assumption. It may be as
little as a few minutes, just enough to prevent more than one person
travelling on the same card.

If it's PAYG, what's the *problem* with several people travelling on the
same card...? Isn't it absolutely the same thing as one person paying in
cash for three tickets for themselves and the two people they're travelling
with?