Roland Perry wrote:
In message , at 16:44:49 on Sun, 11 Mar
2018, Anna Noyd-Dryver remarked:
- They told me that the rest of the railway is still owned and
maintained by the Royal Mail. There is at least the theoretical
possibility of the museum trains doing a longer circuit, perhaps to
the next station, but there appear to be no current plans for such an
expansion. It would obviously need Royal Mail's agreement, and there
would be a significant costs. The current trains may not have the
battery capacity for the extra distances involved.

Problems include lack of emergency exits.

From the site's FAQ:

"Evacuation requirements mean that access to the Mail Rail train ride is
restricted to those who are able to walk unaided on uneven terrain, in a
confined space for up to 100m before climbing 70 steps to the surface."

If the ride was extended to loop round the next station, there would need
to be an evacuation route through that station. The potential walk through
the tunnel would also be much longer, and uphill, to one or other station.

They'd probably also feel obliged to set up additional AV shows on the two
extra platforms traversed. The much longer ride would probably only be run
at less busy times, at a significantly higher price, and aimed at
enthusiasts, not families.