A casual feminist: that was how a prominent British politician, the Member of Parliament Jess Phillips, described Andy Murray on Twitter on Friday.

But, in truth, you can drop the 'casual'; there has been nothing laid-back or understated about Murray's feminism. A committed feminist, more like. As Serena Williams once said of Murray: "Andy really is pro-woman." 

So pro-woman that - and this was a rare move indeed by a leading ATP player - he hired a female coach. Naturally, he supported equal pay for men and women in tennis; he went much further than that, advocating for total parity in all areas, and not just financial. 

Win Wimbledon and you have a voice, and Britain's greatest ever tennis player has called out what has been characterised as 'casual sexism', such as correcting interviewers who had overlooked female players in their questions.

Murray and Laura Robson partnered to win the silver medal at the London Olympics. (Getty)

Murray has also stepped in when affronted by more egregious examples of sexism, both inside and outside tennis, such as when the winner of the inaugural women's Ballon d'Or prize, the Norwegian footballer Ada Hegerberg, was asked by the host to twerk in celebration. "Why," Murray asked, "do women still have to put up with that s---?"  

As Murray once wrote in L'Equipe, the French sports newspaper: "Have I become a feminist? Well, if being a feminist is about fighting so that a woman is treated like a man then, yes, I suppose I have." 

Usually, when a leading tennis player announces their retirement, it provokes reels and listicles of their greatest triumphs and moments and shots. But, in response to Murray's emotional news conference at Melbourne Park ahead of the Australian Open, Buzzfeed published '13 Andy Murray quotes about sexism that proves he's the best'.

In her tribute to Murray, Billie Jean King wrote how his "voice for equality will inspire future generations", and those currently competing on the WTA also focused on the former Wimbledon champion's feminism. 

Read more: WTA stars pay tribute to 'voice for equality' Andy Murray

While the British tennis public will always revere Murray for that golden summer of 2013, when he became the first British man for 77 years to win Wimbledon, the WTA's players admire the Scot for more than just his ability to say boo to Fred Perry's Centre Court ghost.

Former World No.1 Amelie Mauresmo coached Murray from 2014-16. (Getty)

It's funny to think how, in the early stages of his career, Murray was cruelly and mistakenly lampooned by sections of the public for being dull, for supposedly lacking a personality, and yet many now like him as much for the way he thinks and speaks as for the way he hits a serve or a forehand.

Of all the leading ATP players, Murray has consistently shown the greatest interest in women's tennis. And, more generally, in equality. Much of that is down to his mother Judy, who was also his first coach.

"My upbringing means that I'm quite attuned to the whole thing. I came to tennis thanks to my mother. I always had a very close relationship with my grandmothers. I've always been surrounded by women. I find it easier to talk to them. I find it easier to open up to them. It's a crying shame there aren't more female coaches," Murray, a father of two girls, once wrote. 

When Murray worked with Amelie Mauresmo, he became even more of a champion for women.

"Right from the word go, I knew that working alongside Amelie would set tongues wagging. The reason for this is that very few players before me have worked with a female coach. I realised it would create a feeling of suspicion, mistrust and perhaps even negativity," Murray wrote in L'Equipe.

"I didn’t realise, however, that Amélie would find herself up against such criticism and prejudice. The staggering thing was that she was slated every time I lost, which is something my former coaches never ever experienced. It wasn’t right," he added.

"It really opened my eyes when I started working with Amelie. Inequality is something I started to see. And become passionate about. It's opened my mind." 

Such is the affection that many on the WTA have for Murray, the tributes from the women's game were just as warm as those from men's tennis. To borrow Serena's phrase, Murray's achievements justify that tag of "pro-woman."