Traditionally, regulated fare increases were capped at the Retail Price Index (RPI) minus 1. However in 2003 the government changed this to RPI plus 1. This was done as part of the government desire to have rail passengers pay a greater share of the costs of the rail network.
As a result of this change to the rules passengers in Manningtree are paying considerably more. Specifically, the annual season ticket from Manningtree to London at £4,400 is £570 more than it would have been under the previous rules.