City lawyer Elaine Aarons was once on a case she knew would see her working over the weekend. Planning ahead, she informed the client that, as a strictly Orthodox Jew she'd be unavailable from 4pm on Friday to 7pm on Saturday. Unbeknown to her, a colleague had said the same; except he would be available until 5pm. "The client said, 'I'm fine with this, but I don't understand why you're not available from four and he's available until five,'" recounts Aarons, laughing. "I said it's very simple  the difference is, he has a wife!"

In a more-than-30-year career, which has seen her carve out employment law as a specialism, set up the first employment law practice in the London office of Eversheds and co-found the Employment Lawyers’ Association, Aarons has never once compromised her observance of Shabbat or other Jewish practices. That’s remarkable on its own given her field, but all the more so when you learn she has also brought up three children, and, in a professional capacity pioneered everything from a four-day week to working from home, to, most recently, “granny leave”.

As a trainee, Aarons was the first person at Norton Rose to leave early on a Friday. From the outset, her approach was that if she requested this flexibility, she “had to be seen to give back more than I was taking.

“I would work longer hours, I’d be a can-do person. I set myself the task of always surpassing expectations.”

Growing up in Manchester, heavily involved in the Jewish community, and honing her debating skills on Study Group’s national committee, she watched her mother combine being a GP with family life. “She qualified in 1952, she was very pioneering,” explains Aarons. “She was very much my role-model.”

Her late father, a lawyer, was equally encouraging. “It didn’t cross my mind that I wouldn’t do something,” says Aarons. “I didn’t actually think about it very hard, but I didn’t have a default position that my life would involve being at home full time.” Her husband, whom she married while a student at age 19, has always been supportive.”He’s been on the journey with me since the very beginning.”

Climbing the career ladder during the 1980s and ’90s, she was operating in a pressure-cooker environment; with her third child, she took just six weeks maternity leave. She realised something had to give. “I was a convalescent on Shabbat, a mum on Sunday and back to work on Monday,” she recalls. In 1989, Aarons negotiated a four-day week, getting it in writing that she would never be pressured to go back to full-time and that her status wouldn’t be a bar to equity. She was made a partner in less than two years.

The arrangement was unheard of at the time. Yet as Aarons says, she never had a “part time attitude,” regularly working above and beyond in terms of hours. When we meet, at her current law firm, Withers, it’s a Thursday evening, and Aarons still has several hours of work to do — the habit of a lifetime. In reality, she would often work on a Friday and always be there for client emergencies. “If you look at what I have achieved, if you think I’ve got there by having very fixed boundaries, you’d be misunderstanding.”

We discuss the perennial question of women “having it all”. Aarons, who combines her busy schedule with entertaining on Shabbat and Yomtov, would seem a poster child for this. But she says her approach was to work out the best “recipe” for her life.

“I was never going to be Mother Earth,” she says. “I am very much mistress of my home, and I love being with my children but I could never have been at home full-time. So was I sacrificing something, yes, but it was something I could probably never have had. We all have to understand ourselves and work out what’s going to create the best recipe.”

Although she makes it look easy, she admits that her life is a balancing act, particularly between Judaism and professional demands. “You have to be very committed to your religious way of life in order to see it through,” says Aarons, who offers pro bono advice to people struggling with employers who won’t offer flexibility for Shabbat. It’s easier in America but she thinks things have improved in the UK, both for Jews and for parents. She knows that she has been fortunate to have understanding employers. “However much you have a strategy, you’re not in control with whether you’re going to be working with reasonable people.”

A board member of the International Women’s’ Forum UK, Aarons spent a decade on the Taskforce for Talent Innovation focusing on the progression of women and people of colour into the top jobs. She has been a speaker for Aitza, a new Jewish networking group for women in leadership roles, and is co-establishing One Loud Voice For Women, a co-ordinating force for the UK’s women’s networks.

Having blazed a trail in a historically male field — Aarons proudly highlights that, at Withers, 40 per cent of partners are women, but also worries that the career ladder is too rigid at other firms, pointing to the attrition rate of women at senior level — I ask how she feels about the gendered nature of Orthodox Judaism, and the fact that keeping a Jewish home often falls to the woman.

“In an Orthodox home, there are enormous obligations on both men and women, they’re just different,” she says. Her husband davens in a minyan thrice daily and learns Torah every evening. “These are not activities I could absorb, although I do daven in private daily. My priority is to create the warmth, rhythm and essence of a Jewish home. I take great pride in that. We both do what we do well and, together, we create something which is very rich and very valuable.”

While she understands women who want to take a more active role, for example sitting on a shul committee, she can’t support pushing the boundaries beyond what the rabbinical leadership approve. “I believe strongly that the fact we have as a Jewish people survived through the millennia is because we have a formula that works. I understand women who want to participate more in things but on a personal level I’m not looking for that, I feel challenged and motivated by the traditional role I take on.”

In her secular life, she continues to achieve new firsts, securing grandparental leave when her daughter had twins, presenting it as a fait accompli. “Nobody blinked,” she says. Now, with seven grandchildren, she has no intention of slowing down. On moving to Withers she redesigned her career to act almost exclusively for senior executives, a new specialism then.

What’s her secret? “To some extent I’ve been able to imagine for myself what I’ve wanted and it’s been possible to make that into reality. My Jewish values are the first thing to be factored in and everything follows. I do my best to make things work so I don’t have to compromise my values, and if I was faced with a choice I still wouldn’t.”

The one defect in the workplace she hasn’t managed to solve, she says, is the long hours needed to be successful. “I don’t get to as many shiurim as I’d like.”