I was looking to go from London (Euston) to Llanfairfechan 13/10 and back the next day from Llandudno Junction to London.
For London to Llanfairfechan at nationalrail.co.uk I got
Return from £92.90 Buy tickets as 2 Singles from £72.95
More specifically, the outbound ticket was £46.45, leaving 8:10, arriving 11:25 with one change in Chester.
However, as more trains stop later at Llandudno Junction, I wanted to find a later train back.
When I looked for the outbound part as a single ticket, the price was £91.90 for the exact same trains/times.
So is the first ticket advertised as a single ticket not quite a single ticket, is it actually half of a kind of advance (non-open) return?
(Nice to know, I suppose, that it can be cheaper to buy a return consisting of 2 "singles" and throw away one instead of buying a "single single"..)