Thousands of part-time school and council staff have been awarded hundreds of pounds in back-pay after a cleaner refused to give up the fight.
Some 5,000 low paid staff, nearly all women, will share a £4m settlement after a five-year legal battle, backed by public service union Unison.
It argued that Greenwich Council treated these part-time workers less favourably than full-time colleagues.
Greenwich agreed to revise the formula used to calculate holiday allowances.
The issue centred on the calculation of holiday pay for part-time, term-time-only staff.
It was uncovered when school cleaner Julie Stedman, of Plumstead, noticed she was about £35 short when she moved from full- to a part-time status in June 2012.
A new contract allocated her less holiday pay.
She lodged a grievance after her complaint was not taken seriously by her supervisors and says she "kept on at the union" to fight the case.
"I never gave up," says Julie, 52, who has cleaned South Rise Primary in Plumstead, Greenwich, since 2003.
"My husband used to say whenever he came home there were always papers and calculators everywhere.
"I knew it was wrong but nobody was listening.
"I kept arguing my case and arguing and, in the end, they listened and this is where it's got to.
Julie, who earned £722 a month, when she spotted the shortfall, said: "£35 a month is quite a lot of money to lose and the thing is, with school staff, a lot of them have young kids and it's the kids that go without.
"Now I'm really glad that everyone is going to benefit."
The council has now agreed to repay all affected staff at the correct rate back to January 2012.
Unison used European law to bring the employment tribunal claims on behalf of 476 term-time staff - but the corrected formula applies to 5,000 council staff.
Unison assistant general secretary Christina McAnea said: "This is a victory for all low-paid women working in the public sector.
"What started out as just one case could soon be having an impact far beyond south-east London.
"Laws that began life in Europe have enabled Unison to restore justice and ensure that all part-time workers in the Royal Borough of Greenwich are paid the correct holiday pay for the jobs they do.
"Other employers may have made similar errors with their holiday calculations.
"If they have, we'll be on to them to make sure all term-time staff are paid what they're due."
Unison is dealing with a similar case in Suffolk and is aware of two other areas where school support staff have been affected.
Greenwich Council has not commented on the case but sent documents to the BBC showing it believed it to be less costly to settle the claim before it reached an employment tribunal.
Julie says she does not know exactly how much she will receive in the payout.
But she plans to put it towards a family holiday.
She adds that she will be keeping a close eye on the council to make sure the back-pay is correct.
"I haven't come all this way for it to be wrong now.
"I always used to say to my daughters, 'Keep this, keep that.' I've still got all my wage slips.
"I think I am going to change jobs and become an accountant!"