Neil Williams wrote:

Why not just withdraw Saver tickets completely? Surely Oyster has
superceded them to any practical extent?

Too much faffing about for the occasional visitor, especially tourists.
You have to pay 3 quid deposit to get an Oyster in the first place, then
claim a refund when you hand it in.
--
Joyce Whitchurch, Stalybridge, UK
=================================
Old enough to remember something
similar to Saver tickets in Glasgow
some twenty-odd years ago