They set out to fight for a fair deal for themselves; they ended up changing the world of work for generations of women. Now the 187 women machinists from Ford's flagship factory in Essex are to be celebrated in Made in Dagenham – starring Miranda Richardson and Bob Hoskins – which opens in cinemas across the UK this month. This weekend the man who worked behind the scenes as history was being made spoke, in a rare interview, to the IoS about the part he played in it.

The former transport union official Frederick Blake, now 91, recalled: "When the girls came down to see Barbara Castle [then employment minister] I was asked to sit in a separate room because she wanted to see them on their own, which is fair enough." Mr Blake was described by newspapers at the time of the strike as "the leader of the new suffragettes".

"Although I was in charge of the union for the Ford factory I stayed in the background because I didn't want people to think that a man was leading the women," he added. "I was asked by the bosses to tell them to go back to work so we could keep negotiating, but I wouldn't do that until we had a good settlement because there were men doing the same job as them being paid more. It wasn't fair."

Mr Blake explained that he was an advocate of women's rights long before the strike that made history: "When I came home after fighting in Burma in the Second World War and saw the damage that the bombs had done to the country, I thought, 'Why don't the women get medals for what they've had to put up with, too?' That's what first made me think about equality."

When women machinists at Ford's Dagenham factory downed tools in 1968 in protest at the fact that they were classed as unskilled workers, while male colleagues doing the same job were thought to be skilled and paid much more for their efforts, they couldn't have imagined the ramifications.

The three-week strike brought production at the factory – which was the focus of the UK car industry at the time – to a standstill, and the dispute was resolved only when Barbara Castle was brought in to negotiate a settlement.

The Ford machinists went back to work after agreeing to be paid 92 per cent of male machinists' wages, and the strike speeded up the introduction of the Equal Pay Act of 1970, which made it illegal to have different pay scales for men and women.

The new film which dramatises these events has been compared to the modern British classics Billy Elliot and The Full Monty. With the Calendar Girls director, Nigel Cole, at the helm, the film stars a clutch of high-profile British performers, including Rosamund Pike as the factory boss's rich wife, and Sally Hawkins as the strike leader.

However, some of the women workers who took part in the strike have accused the film-makers of "sexing up" their story.

"At the beginning of the film they strip off on the factory floor; we weren't allowed to strip off, and we had too much pride to do it even if we were," said Gwen Davis, who was a 35-year-old worker in the Ford factory at the time of the strike. "It is very exaggerated, but still good."

The women on the picket line in 1968 endured jeers when a photographer snapped one of their banners declaring "We Want Sexual Equality" partly unfurled, so that it read "We Want Sex".

The machinists were also supported by the union representative Bernie Passingham, and many had the backing of husbands who worked in the factory. At the time the practice of women being paid less than men for the same jobs was widespread – a tradition that hasn't entirely died out. In 2010 women working full time in Britain still earn on average 16.4 per cent less per hour than men working full time.