Hundreds of workers in the country's biggest fire authority are in line for a payout after unions won a four-year campaign over a long-term wage deal.
Unison and the GMB announced that the Court of Appeal had found in their favour over a 2.5% pay rise for staff at the London Fire Authority, including clerical, administrative and call centre workers.
The unions accused the authority of refusing to honour the third year of an agreed pay deal that would have given staff the 2.5% increase in April 2009. The decision will be worth hundreds of thousands of pounds and will affect past and future pay increases, said the unions.
Officials said some low paid workers earning just over £13,600 a year missed out on an agreed pay increase.
Dave Prentis, general secretary of Unison, said: "Trust is an integral part of any negotiations and I am pleased that we have been able to deliver pay justice to our members at the authority. Times are tough for many public service workers without being denied a pay rise that they are entitled to.
"It has taken a four-year legal battle to win this case. Without the union to fight this case the employers would have got away with a gross injustice and members and their families would have lost out."
Unison branch secretary Tony Phillips said: "Fire and rescue staff are delighted with the successful outcome of this case. We hope that it will show unscrupulous employers that they cannot get away with reneging on written agreements with trade unions when they no longer suit them."
Paul Maloney, of the GMB, said: "This is great news for our members."
A spokesman for the London Fire Brigade said: "The disagreement stemmed from the fire authority's interpretation of the pay formula for the year 2009, which differed to that of the unions. There was no deliberate attempt to deny people any part of their wages, it was a difference of interpretation, which has been found in the unions' favour. A committee of the authority will now be consulted on the way forward."
The GMB said its members were in line to receive back pay of between £750 and £2,500 each, with another rise in the coming financial year worth between £182 and £664.