The strike on Tuesday by council workers in Birmingham has highlighted the difficulties councils face in ending the historic inequalities in pay between men and women.
About 3,000 striking council workers held a rally in Birmingham
According to recent statistics women are paid around 17% less than men in the same full-time jobs. In part-time jobs the difference is even more stark - an astonishing 36%.
And yet the UK has had equal pay legislation in place for the best part of 40 years.
So what on earth has gone wrong? Why have women waited so long to get equal pay with men?
The truth is it wasn't until 1997 that local government and trade unions came together to try to force through change.
The result of their efforts was the single status agreement. It was meant to kickstart deals in councils across the UK.
But it took a revised deal in 2003 to really concentrate minds.
A deadline of April 2007 was set for new pay deals to be agreed. But when that self-imposed deadline passed, fewer than a third of councils had managed to put new pay arrangements in place.
The picture was complicated further by an EU ruling in 2004. It meant those who had been underpaid had the possibility of claiming back pay for up to six years.
Some estimates suggest that has opened a financing black hole of close to £3bn.
That's left unions with a dilemma.
They know many councils can only fulfil their pledge to deliver equal pay, fully backdated, by cutting some jobs or services.
So instead they've entered into negotiations with councils in an attempt to get the best deal for workers while safeguarding jobs. In some cases they've recommended deals with just two or three years back pay.
Some lawyers believe they could do better for council staff. They've taken cases against councillors and union officers, and have managed to win much bigger rewards.
Such cases are now said to be clogging up the tribunal system. Some fear the estimated 50,000 claims in the system could soar to perhaps 150,000 by the end of the year.
Staff at Birmingham City Council are angry at plans to restructure wages
Trevor Phillips, chairman of the Equality and Human Rights Commission, recently called for so-called representative actions which would see many cases heard at the same time to tackle the backlog.
The process of equalising pay has also been complex. Councils have had to carry out an evaluation of every job, checking the skills required.
Other factors also come into play, such as does the job involve working with the public or in dangerous situations? Each job is given an overall score. Jobs with similar scores end up having similar salaries.
In general it has meant that women in unskilled jobs have seen a rise in pay. Men in jobs with a similar score have seen their pay fall.
Where workers' jobs have been reassessed, the result in the pay packet has been mixed.
According to the Local Government Authority about 40% of staff end up better off. Another 40% stay roughly the same. But typically 15-20% of staff find they are facing a drop in salary and these tend to be men.
But as women make up 75% of the local government workforce, the irony is that many have also seen their pay package hit in the process.
Even women in similar jobs have had different outcomes.
Janey Simmons is a teaching assistant in Birmingham with two years experience. Under the new arrangements she'll receive a £600 lump sum in back pay and about £500 extra in her annual salary.
But other colleagues who have worked at the same school for much longer are not getting a pay rise.
Ms Simmons joined the demonstrations in Birmingham to protest at how the re-grading had been forced through.
"I've been told I'll gain a reasonable sum backdated. And I'll also have an increase in my salary, which is good news for me," she said.