TfL are very fond of telilng us that we can top up our cards online at
anytime. True, and great if you live on the tube.

Not so good if you don't.

Here's an idea for a workaround though, which simply involves
maintaining a prepay balance and a tweak to the system.

Let's say my oystercard expires and using the website I purchase a
Travelcard, to start on Monday.

On Monday morning I take a bus to my designated station, and the fare
for that journey is deducted from my prepay balance.

Upon arriving at my designated station, the Travelcard I purchased is
downloaded to my oystercard BUT the bus fare is also credited back to
my prepay balance, as I had already bought a ticket to cover it.

Could it work?