When purchasing a new ticket for an oyster-card online, the ticket is added
to the card when going through a gate at some nominated station... all well
and good.

What happens however when there is a gap between dates covered by the
tickets, such that the new ticket is actually being purchased after the
previous one runs out? How can I pass through a ticket gate to renew the
card, if I have no valid tickets on the card?

Should I just turn up to the station and try it on a barrier a few days
before the new ticket begins? I presume it would reject the card, but would
it still write the new ticket?

Ta.

J.