There’s a good story about Nicola Mendelsohn at the start of her career. Setting out for her final interview for a graduate trainee job at an advertising agency, she shut the front door of the house in Hendon where she’d been staying and waited for the taxi she’d ordered.

She waited and waited. No taxi arrived. What was she to do? These were the days before mobile phones and, as a Mancunian, she had no local knowledge. But she was determined to get to the interview. So she flagged down a passing car and told the driver, “You have to help me!”

Luckily she’d stopped a nice old lady and not an axe murderer. Mendelsohn got to her interview and got the job. That led to a very successful career in advertising, culminating in her current post as Facebook’s boss in Europe, Africa and the Middle East.

The story illustrates some attributes that have been helpful in her life since then. Determination is one and resourcefulness another. She’ll take risks, if necessary, to reach her goal. But most of all, it displays a basic optimism about life. And right now, living with an incurable disease, she needs it more than ever before.

We meet at one of Facebook’s offices in London. I’m surprised that visitors have to sign a non-disclosure agreement and so am not sure if I can report that the building is spacious and bright, there’s a help-yourself pick n mix wall of sweets and a coffee-dispensing corner, with lots of chocolate. The walls are hung with posters: ‘Nothing at Facebook is somebody else’s problem’, ‘Be the nerd’, ‘Remember, meetings were made for laughter’. You get the picture.

Before meeting Mendelsohn, I’d had a quick snoop at her Facebook profile (we have, it turns out, 19 friends in common). From the posts she makes public I see that she has a beautiful family , three sons and one daughter, lining up in her cover photo, all dressed in white, with her and her husband, the Labour peer Lord Mendelsohn.

Her life (or the bit she makes public on Facebook) is social and very busy with dinners and simchas and working trips abroad. But despite all this she has carved out the time to create a new charity, one which quite literally could save her life.

Unless you live in a cave, you’ll have seen the coverage of the charity’s launch (not least in last week’s JC), because the reach was phenomenal — more than 150 million people, she tells me with pride. The launch took place jointly in London and New York and, of course, on Facebook and its picture-sharing app Instagram where celebrities piled in to help raise awareness and funds for Follicular Lymphoma (FL), the blood cancer she was diagnosed with in 2016 at the age of 44.

There is currently no cure for FL and her aim is to find one. “I absolutely believe there is a cure out there,” she says. “What this disease has lacked is awareness, both publically and in the medical world as well. And the funds to make it happen. So that is the intention.”

Big data is something that we often hear about in a negative way, when considering the influence of internet giants such as, well, Facebook but Mendelsohn believes firmly that its power can be harnessed to help people like her.

“We want something that is genuinely transformative. We’re not looking for iteration around the edges.

“I’m really interested in how big data and the applying of machine learning can help to solve the problem. So much of medicine will be about personalised approaches, So many of the personalised treatments do come from blood cancers and then extend out.”

In the meantime, the charity’s new website (www.theflf.org) and the support group that she jointly runs on Facebook will help people know what to ask and what might be possible when they see their doctors. “In London we have access to top specialists,” she points out, “which is not the case for most people.”

Some people in the group have not told anyone of their diagnosis, but Mendelsohn never considered keeping it secret. Eventually she wrote an article for the Sunday Times, explaining the horror of discovering that a small lump in her groin had eventually proved to be the only symptom (some people have none at all) of an incurable disease.

Telling her children — now aged between 22 and 14 — was the worst part. Her youngest asked if she was going to die. “It is not a conversation I could ever have imagined having with them, not even in my worst nightmares, until it hit me in the face,” she wrote. “It was the hardest moment of my life.”

Family support has helped her cope but also there’s her optimism. “One of the things my friends say about me is that one of the things that I’ve always done is to practise gratitude, to live in the moment and to be grateful — incredibly grateful — for the life I have.” Last weekend, at a close friend’s batmitzvah, all her children were there.

“I don’t take that for granted that my four grown up children would want to come, would want to be with us and celebrate. That matters hugely to me, that whole sense of family values.

“A cancer diagnosis is a massive kick in the teeth that can easily take you to the darkest of places. And it did. I’ve been really clear about that. But I didn’t want it to define my life and I didn’t want it to be the thing that would be all encompassing of every aspect of my life.”

Judaism is, and has always been, at the centre of her life. “At the heart of Judaism is family and the wider family of community,” she says. “I know that I’ve never had to think about the fact that I would go through this alone — it wouldn’t even occur to me — and yet for so many people it is.”

She’s been struck by the loneliness of some members of the FL support group. “They’ve got no family, they’ve got no friends, they’re going through the worst thing in their life alone. If you practise Judaism, that would never happen. There would always be someone on the worst days making a pot of chicken soup for you.”

In this way — creating communities for anyone who needs one — Facebook in particular and the internet in general is a powerful force for good, she believes, and one which aligns very much with her Jewish values.

Growing up in Prestwich, Manchester, her parents instilled into her a sense of community and she and her husband are active in Finchley United Synagogue. “My parents taught me the value of volunteering and I spent many Sundays in my youth at Heathlands, the old age home, singing terrible songs because I have the worst voice. I remember marching for Soviet Jewry, in those days, in the 80s. Living a good life with good values, surrounded by family, there’s nothing more important than that.”

She’s the daughter of the legendary caterer Celia Clyne, who went from cookery teacher, to running a restaurant in the Jewish Cultural Centre, to the banqueting queen of the north. The catering business started when Mendelsohn was 11, “so, growing up around a mum who was working was totally normal.” Her grandmother also worked with her grandfather, selling haberdashery, fabrics and trimmings on the market. Her father also works in the catering business and so does her older brother, Mark. Her younger brother Adam runs the media company Coolr and was actively involved in launching the charity.

She wanted to be an actress, and studied English and Theatre Studies at Leeds University where she — quite literally — had a ball. She is still proud of her efforts organising “possibly the largest JSoc ball ever— for more than 1,000 people”, raising thousands of pounds for charity. No prizes for guessing who the caterers were. She also met her husband and they married soon after she graduated.

She has no regrets about abandoning her acting ambitions, recognising that it was hard to sustain a career in theatre if you are shomer Shabbat. She loved advertising’s combination of creativity, problem-solving and results. When she started out, in pre-internet days, a client might want a TV ad and a print ad. “If I were doing the same job now,” she says, “I’d be making thousands of pieces of content that would be deployed in so many different areas.”

The internet has changed everything . “If you don’t think it’s impacted an area of your life— it will do.” She acknowledges that means upheaval and change, which many fear, but insists that the positive outweighs the negative.

Facebook is actively listening to its critics, she says (only last week, Sasha Baron Cohen accused Facebook founder Mark Zuckerberg of facilitating “hate and violence”), and has invested “billions and billions” on machine learning so that hateful content is taken down or, ideally, never made public at all. The company employs 35,000 content moderators, and 99.9% of terrorism-related posts are picked up before they are made public, she says, figures which made her “very proud.” The company’s efforts can be stymied by the lack of international agreement on what constitutes hate speech. But anything promoting violence is taken down immediately. Facebook has been working with Hope not Hate, the Community Security Trust and the Board of Deputies to make sure Jews know how to report antisemitic posts or threats.

As to more general concerns about data mining, she urges people to check their privacy settings. ”We’ve made a lot of changes in the last few months, making sure that people are clear about the information that they have on Facebook and what they want to put out and share as well.”

Right now, of course, the focus is on the election. Facebook takes political advertising as “it isn’t for a private company to say what a politician should put out there.” Political parties and individuals must register with Facebook and make clear where their ads are coming from, so “the person looking at it is really clear that it’s political advertising.” The ads are then archived and kept for seven years. This system gives more transparency and information than ever before, she says.

We’ve got one minute left in her busy schedule — she’s due to speak at a training event and later in the week is flying off to Sweden — so I attempt to breach her personal privacy settings. She’s married to a Labour peer — her husband was Tony Blair’s fundraiser — and he recently spoke out against antisemitism in the Labour party. They live in Finchley, the constituency where Luciana Berger is standing for the Liberal Democrats. How will she will be voting, I wonder.

“Voting is a private matter,” she replies and I think that’s that. But then she adds, “I abhor racism. I’ve fought my whole life against racism. It’s an interesting election for everyone.”