2016 has become the summer of strikes. At the heart of the disputes, involving Southern Rail, Eurostar, ScotRail and Virgin East Coast, is Mick Cash, the general secretary of the RMT Union. Unlike his predecessor, the late Bob Crow, Cash is a relative unknown outside of the transport world.

But despite his low profile, the 56-year-old has hinted out how he approaches disputes. "We negotiate first, we seek to get deals, but if we can't we give our members the opportunity to have their say," Cash told The Guardian in 2014.

His detractors, however, have a different take on the RMT's efforts. Andrew Allison, head of campaigns at The Freedom Association, has accused the union's leadership of revelling in their "bully boy image".

However, their alleged confrontational approach seems to be working – at least when it comes to membership figures. At a time when trade union membership continues to drop across the UK, the RMT has seen its ranks swell. The union's membership stands at more than 83,000, up from 77,000 in 2012.

The surge comes amid a crackdown on from the Conservative government in the shape of Trade Union Act, which has introduced a statutory turnout threshold of 50% for a strike ballot to be eligible. The legislation is so controversial Brexit Secretary David Davis once compared it to anti-trade union rules under Spanish dictator General Franco.

For his efforts, Cash has a total remuneration package of more than £137,000 ($177,572), a rate which has drawn criticism from right-wingers.

But Cash's salary is commensurate with the pay packets of general secretaries who lead trade unions of a similar size to the RMT. Sally Hunt, the chief of the University and College Union, is awarded more than £134,000 and her union boasts around 100,000 members.

Either way, Cash has come a long way since he first joined the National Union of Railwaymen around 35 years ago.

A long-term supporter of Labour, he served on the party's governing body, the National Executive Committee, and backed the Iraq War, leading to one activist from the Trotskyist group Alliance for Workers' Liberty branding him "right-wing".

Before that, he served on Watford Borough Council, having grown up in the town and being an avid supporter of Watford FC. Nigel Bell, a fellow Labour councillor at the time, told IBTimes UK Cash was always "friendly and outgoing" and was "respected across the chamber when he rose to speak."

More recently, Cash's union, despite no longer being affiliated with Labour following its expulsion in 2004, has thrown its support fully behind Jeremy Corbyn's campaign to retain the party's leadership, with both men wanting to re-nationalise Britain's railways. However, Cash's union took a different stance to the left-winger over the EU referendum.

The RMT joined fellow transport union Aslef and the Bakers' Union in backing a Leave vote at the historic ballot, arguing that Brussels is a "bosses club" and warning against the secretive Trade and Investment Partnership (TTIP) trade agreement between the EU and US.

Mick Whelan, the general secretary of Aslef, has known Cash for more than two decades. "Mick, overtly, does what is necessary for his trade union," he told IBTimes UK. "Do we clash? We don't always agree on everything, but I would say on more than 90% of things we do."

Bob Crow and Tony Benn
Bob Crow and Labour firebrand Tony Benn were both critics of the EU Getty