Michael R N Dolbear wrote:

All National Rail ticket officers are supposed to suggest a cheaper
ticket if such exists and, eg, Which? will sic their mystery shoppers
on them and berate them if they fail.

They are required to offer the cheapest *available* through ticket for
the journey being made. However, that doesn't mean that staff are
expected to know every possible set of tickets for a given journey.

It also depends on what Ticket Issuing System that station uses. Cubic
FasTIS, for example, will show Travelcards where appropriate, in
addition to point to point tickets, whereas other TIS will only show the
point to point ones.

Having said that, Colin's example of Cambridge to Putney doesn't require
rocket science to work out that a Travelcard is cheaper...

Cheers,

Barry