Section
4.2.2 Excess procedures: Upgrade to First Class of our
RailUK Fares & Ticketing Guide tells us that to excess "
ONE portion (Outward or Return) of a Return ticket, the charge is the
DIFFERENCE between the price already paid and the
SUM of the appropriate Standard Single for one leg and the appropriate First Single for the other leg. If cheaper then the
FULL difference between the Standard Return and the First Return (as if upgrading both legs) is charged."
In this instance, the sum of the appropriate Standard Single for one leg (
SOS £103.00) and the appropriate First Single for the other leg (
FOS £142.00) is £245.00. The difference between £245.00 and the price already paid (£113.50) is
£131.50.
The full difference between between the Standard Return and the First Return is FOR £284.00 minus FOS £142.00 which is £142.00.
The full difference between between the Standard Return and the First Return is
FOR £284.00 minus
SOR £113.50 which is
£170.50.
The amount charged is the lower of the two sums in
bold, that is £131.50.