I've posted this before, but if you buy a ticket at Paddington to
Clapham Junction, it gets printed as a "London Terminals" to Clapham
Junction, price £2.10 (£1.40 with a goldcard), and it works in the
tube barriers at Paddington and Waterloo.

The screen specifically states "London Paddington to Clapham
Junction", route "any permitted", for the avoidance of any doubt. No
maltese cross though.