The Court of Appeal has reduced the sentence handed to former City trader Tom Hayes for his part in fixing the Libor rate by three years.

Hayes had his sentence cut from 14 years to 11 years yesterday, however the court upheld the guilty verdict handed to Hayes in August this year.

In their decision Lord Thomas, Sir Brian Leveson and Lord Justice Gloster said Hayes' criminality was "grave" and as such the sentence needed to  "deter others from criminality that is often hard to detect and has such a damaging effect".

They added: "It [the offence] continued over a very substantial period of time. It involved conspiracies with several different parties and several different types of market manipulation."

Given Hayes' diagnosis of mild Asperger's, his age and his position below management level, the judges said that the initial sentence "was longer than was necessary to punish the appellant and to deter others".

Hayes was the first person to be convicted of rigging the Libor lending rates in the City following action by the Serious Fraud Office (SFO).

At the time of the verdict white collar lawyers said it would be a major boost for the SFO which has been dogged by serial errors, failed prosecutions and critical independent reports, culminating in a combined payment of damages and costs totalling £7.5m to billionaire property developers the Tchenguiz brothers in July last year.

At the appeal Hayes was represented by Charter Chambers Neil Hawes QC, 33 Chancery Lane's Christopher Convey and Catherine Collins, who were instructed by Cartwright King Solicitors. The SFO turned to 9-12 Bell Yard's Mukul Chawla QC alongside Red Lion Chambers' Gillian Jones and Max Baines for representation.