Whenever Sir Keir Starmer is profiled by the national press much is made of the first name he shares with Labour pioneer Keir Hardie.

The story goes that his parents, staunch Labour supporters, proudly named their first-born son after the Scottish socialist hero.

But it is not a conversation Sir Keir has ever actually had with his parents and it is a discussion he will never have with his elderly mother.

She has not spoken a word for five years as the result of a devastating illness which she has battled for half a century, something Sir Keir has previously refused to speak about publicly.

But with just six weeks remaining before he is expected to stroll into the Commons, the 52-year-old – Labour’s parliamentary candidate for safe seat Holborn and St Pancras – has decided to open up about his mother’s life-long struggle with Still’s disease, a rare and incurable condition which causes painful swelling of joints and organs.

“She is very ill and has been very ill for over 50 years,” he said. “She’s been on steroids for 50 years to deal with the disease. There have been huge and very damaging side-effects.

“She’s been in and out of high-dependency units for as long as I can remember. It was something we grew up with. I certainly have seen the NHS from the inside for decades.”

Sir Keir was brought up in Oxted, on the Kent-Surrey border, where his parents still live to this day. His father, a former toolmaker, is now a full-time carer for his wife, who worked as a nurse in healthier days.

“She’s been a massive fighter all her life. She managed to walk and work for many years,” said Sir Keir of his mother, who recently had her leg amputated.

As a barrister, Sir Keir has reached the apogee of his profession. He served as director of public prosecutions (DPP) for England and Wales between 2008 and 2013, before being knighted a year later for services to law, notably in recognition of his work to abolish the death penalty in several Caribbean countries.

He is a good friend of Ed Miliband and is expected to land a ministerial role in a future Labour government.

But he insists his working life has never been motivated by personal ambition, rather a sense of “purpose” and determination, for which he credits his mother.

“I wanted to be a human rights lawyer to change things for individuals who most needed my legal help and assistance,” he said.

“I became DPP because I wanted to change and improve the way we prosecuted cases. It’s always been a purpose-led route through my career. Doing things because there’s a job to be done.

“I think a bit of it comes from the determination of my mother. What I can’t stand is when people walk around a problem and can’t solve it so I have resolved not to do that.”

Today, Sir Keir and his wife live in Kentish Town, with their six-year-old son and four-year-old daughter.

He is an Arsenal season ticket holder and plays five-a-side football with friends twice a week in Muswell Hill.

Asked what he makes of the suggestion he is something of a housewives’ pin-up, the father-of-two winces.

“It’s not something which I take very much notice of, to be honest.”

But he is unequivocal about the discomfort caused by his knighthood. There is no mention of “Sir Keir” in his campaign literature.

“I’ve never liked titles,” he said. “When I was DPP, everyone called me director and I said, ‘Please don’t call me director, call me Keir Starmer.’ It’s a very similar battle now.”

He is preparing to leave law and Doughty Street Chambers, the law firm he helped found in 1990, for good in May and is currently completing a review of sex abuse prosecutions brought against alleged IRA members in Northern Ireland.

“I’m winding down my cases which is why I’m so busy,” he said. “I will no longer take on cases as a lawyer.

“I gave up Doughty Street Chambers completely when I became DPP and I’m ready to give it up again. It’s sad in the sense I will be giving it up for good.

“I’ve got my eyes set on winning Holborn and St Pancras and then doing whatever I can do to help a Labour government change the things that need changing. I will continue for as long as I can usefully try to change things.”