From the moment Hannah Shabathai became president of the charity "Save a Child's Heart", in Switzerland, the seed of an idea grew in her mind: a way to combine her two passions, SACH and music; a concert with world-class pianist Evgeny Kissin. The retired United Nations worker is a lifelong fan of the musician, having studied piano herself for 15 years at the Geneva Music Academy.

Asked how she managed to achieve such a coup, this former north London Jewish girl makes extensive use of the word "chutzpah".

Already retired from her career in the World Health Organisation at the United Nations, Shabathai's attention was caught by Israeli charity SACH a few years ago when she visited its medical centre and children's home in Israel.

The charity, which celebrates its 20th anniversary this year, offers free, life-saving heart surgery to children from developing countries. Almost half of the children treated are Palestinian and they have helped over 2,300 children from more than 48 countries.

Since becoming Switzerland SACH's president, Shabathai has been responsible for getting the charity recognised for official relations with the UN.

"I visited the SACH hospital in Israel," she recalls, "and I was enraptured by its humanitarian work.

"I'm just very keen to do something useful in my life, particularly saving children's lives. I don't have children of my own so I feel it is a very satisfying endeavour. And our work is very tangible, you actually see the child that you save."

The story of how she persuaded one of the world's top pianists to agree to a private charity concert took root in Italy, back in 2013.

"I call this story 'Umbria'," Shabathai begins mysteriously, before explaining: "Two summers ago, I attended a kosher cooking course in Umbria with a friend.

"She was grateful for my friendship, particularly during a grieving period in her life, and asked me if there was anything she could do for me to show her appreciation.

"I immediately responded: 'introduce me to Evgeny Kissin' (he was a relative of hers). And she accepted.

"My friend wrote to Evgeny and explained that I had been good to her and perhaps he could help my charity.

"He responded positively. However, to establish contact with Kissin proved extremely difficult. He is a superstar and although he is very well-meaning, he is understandably very limited in his free time."

The Russian Jewish pianist lives in the UK and France, and is well known for speaking out in support of Israel. In 2013, in fact, he became an Israeli citizen.

He is notorious for rarely giving interviews, so getting him to agree to a meeting was bound to be a challenge.

Former Hasmonean Girls pupil Shabathai spent months emailing back and forth with the musician:

"I tried many, many times to suggest a rendezvous. You know, I really had a little bit of a chutzpah."

Finally, Kissin suggested she join him backstage after his concert at Verbier Festival, where he is a regular.

"I was very excited," she says, "and I imagined there would be me and Evgeny Kissin, and perhaps a bottle of champagne, backstage, and of course the scenario proved to be very different.

"I find myself queuing up with at least one hundred young girls, pushing and shoving to get autographs.

"So I pushed myself forward and identified myself to Evgeny, I went straight to the top, I really shoved and pushed.

"He was very polite, but very distant. Later on, I appreciated that this is because he is an artist.

"He's just performed and therefore he is very involved in his music; he's still in another world.

"So I went back to Geneva disillusioned."

Having almost given up hope, Shabathai was persuaded by a friend to try again.

So a second cycle of emails began, back and forth. But with no meeting confirmed Shabathai took matters into her own hands and told the pianist she would come to London to see him, booking her flight before he could change his mind.

They agreed to meet at the exclusive Lanesborough Hotel in central London for afternoon tea.

"I'm sitting at the Lanesborough for this 5pm meeting and I'm looking at my emails thinking he's going to cancel. I was really nervous about this whole thing. At five o clock on the dot, he arrives. He walks straight up to my table and we cordially, formally, say hello," she says

After a stiff few minutes of small talk, the pair clicked and Shabathai found herself laying the foundations of a firm friendship:

"After the first, formal 10 minutes, all of a sudden, I don't know what it was, we got on like a house on fire. We were there for three hours. We talked of music, Israel, life, everything. It was just wonderful.

"I said, 'will you consider performing for SACH' and he immediately said: 'Absolutely'. Then I mumbled awkwardly: 'How much do we pay you?'"

But Kissin refused payment.

"I was absolutely delighted," says Shabathai. No one at SACH or in my family could believe it. I had established, not only that, but a fine friendship as well."

It has taken a year from gaining the pianist's trust to actually finalising the concert, which will take place on March 14 at Conservatoire de Musique de Genève.

The private concert for 300 people will be followed by a dinner with the artist at the Grand Théâtre de Genève - the Geneva opera house - the venue having been donated by the state of Geneva, where, according to Shabathai, the palatial rooms usually cost tens of thousands of Swiss francs to hire.

Having managed to secure sponsorship to cover costs, all of the proceeds will go to SACH.

Evgeny Kissin explained to the JC: "The reason why I'm doing the concert is so simple and obvious. It's just because it's a very good and important cause."

Hannah Shabathai is ecstatic. "I have always been a fan of Evgeny's," she purrs, "I think he is the greatest.

"I couldn't have wanted anyone else to do it," she says, adding: "And I can tell you this is not the last one. It has opened doors to other superstars."

Although she wouldn't disclose who she has her sights set on, I have absolutely no doubt she will succeed.