Terry Casey wrote:
A friend went to Goodmayes station on Friday morning and asked for a single
to Southall, for which he was charged £5.10. He set off via Liverpool Street
and Paddington but when he got to Southall he was told his ticket was
invalid and he would have to pay again - £3.10.

snip

Unless there is a way that he could have been sold the wrong ticket for the
correct fare at Goodmayes, I feel he has been the victim of First Great
Western incompetence and that it is to FGW that he should complain. Is my
assumption correct?

The trouble here is the introduction of zonal ticketing within the
Travelcard Area and an associated lack of training.

There are two different types of zonal fares that apply now. First up,
you have the "rail only" zonal fares, and then there are the
"Train-Tube" fares.

The latter are the only variety valid on the tube and are issued from
the origin station to the appropriate zonal combination (or vice versa).

So, in this example, your friend was issued precisely the correct ticket
(namely Goodmayes to U1234), and the member of staff at Southall was
talking through his backside.

Other examples:

Surbiton to Maryland would be issued as Surbiton to U1256
Selhurst to Holborn as Selhurst to U1234
Victoria to Morden via Balham as London Terminals to U1234

It's covered in Section L of the National Fares Manual, which can be
downloaded via the ATOC site. [1]

HTH,

Barry

[1] https://www.atoc.org/retail/_downloads/NFM95/NFM95_Common_L.pdf