He forged a glittering international career that turned him into a global icon, is one of the most marketable footballers in the world and has enjoyed personal fulfilment as a doting dad to four children.

But if you ask David Beckham what really drives his personal and professional success, the answer is refreshingly simple: the support of his family, including his Jewish grandfather.

Beckham, 41, told a 200-strong audience at JW3 on Tuesday night that he was “very lucky that from a young age, my parents, sisters and grandparents supported me.”

Referring to his Jewish maternal grandfather, Joseph West, who died in 2009, the former England captain added: “My grandad would follow me everywhere to watch me play.”

Beckham, who appeared at the Finchley Road venue in conversation with Kirsty Young, as part of the Alan Howard Foundation/JW3 Speaker Series, added he feels partly Jewish and although he was not brought up in the faith, recalled that “whenever [my grandfather] went to synagogue, I was a part of that.”

The oversubscribed event, for which JW3 received 700 applications for just 200 tickets, largely focused on Beckham’s involvement as an ambassador with UNICEF UK, since 2005. The many countries he has visited in that time include Sierra Leone, Cambodia, Papua New Guinea, the Phillipines and South Africa.

He also spoke about 7: The David Beckham UNICEF Fund, which he launched last year to focus on specific issues involving young people around the world.

The audience heard how Beckham recently returned from a trip to Swaziland, where UNICEF is supporting some 56,000 children who have been orphaned by AIDS. He also spoke about his visit last year to Djibouti, where poor health resources result in one in 14 children dying before their fifth birthday.

While he has been engaged with a number of charities over the years, Beckham recalled how UNICEF made a particular impression on him, ever since he first visited a woman’s centre in Thailand with Manchester United, 15 years ago.

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Beckham appeared in conversation with Kirsty Young, as part of the Alan Howard Foundation/JW3 Speaker Series

“I knew that’s what I wanted to do when I finished playing, to be involved with a charity that does so much for children around the world.

“Even before I had children I always really cared about children and their future. My mum tells me I was always like that and I say the same about my children.

“They are so affectionate and have a natural gift with kids. So when Kofi Annan contacted me to become an ambassador it was very emotional and a proud moment for me.”

Married to former pop star and fashion designer Victoria Beckham since 1999, the talented sportsman said he takes the time to explain his UNICEF work to their four children, Brooklyn, 17, Romeo, 13, Cruz, 11 and Harper, 4.

“I want to sit down and talk to them about where I’ve been and the causes we’ve helped. They know what I do and what Victoria does [as a UN goodwill ambassador]. It’s important for the kids to see that. I want them to know that I want to work hard for all the children and their futures.”

Away from his charity work and his much-lauded success on the pitch, Beckham spoke about the pressure of growing up in the constant glare of the media and paid tribute to his Manchester United manager, Alex Ferguson.

He also described leaving Manchester United in 2003 – having won six Premier League titles, two FA Cups and one Champions League crown during his career with the club – as “one of the lowest points” of his time in football.

“I physically couldn’t watch them play for three years – and I’m the biggest Manchester United fan,” said Beckham.

When Young asked if he was “hell to live with” during those years, he prompted laughter from the audience by responding: “You should ask my wife, but yes, I think I was.”

He equally cited getting sent off for kicking Argentinian player Diego Simeone during the 1998 World Cup as “the hardest time”, not just because of the personal vitriol against him that followed from the media and fans, but also because “my family were being harassed as well.”

Beckham took a few moments to help another cause close to his heart – the Make-a-Wish Foundation – and signed football shirts for a group of terminally-ill children

When asked what he had learnt from the situation, Beckham quipped: “I learnt not to be so obvious about a kick! But also, it made me stronger as a person and a player.”

He added: “I’m not glad it happened, but maybe I wouldn’t have had this life and career if it hadn’t, it really made me grow up.”

Alongside the lows there have of course been immense highs, including being awarded an OBE aged just 28 for services to football, in 2003.

He took time to reflect on England’s chances in Euro 2016 and said the team’s first game against Russia was “a great, strong, performance”. Beckham also described Roy Hodgson’s current line-up as “a group of young, raw and talented players.”

When asked if he would one day consider becoming a manager, Beckham ruled it “for the moment”.

“That might change in five years’ time,” he continued, “but at the moment, my passion is Unicef and being a part of this organisation. That’s what drives me. I’m passionate about the game and always will be, but not being a manager. For some people that’s what makes them tick, but for me it’s my charity work that makes me tick”

Towards the end of the night, Beckham divulged light-hearted anecdotes about his personal life, including that he was introduced to Victoria, thanks to the matchmaking efforts of Manchester United’s Jewish non-executive director Michael Edelson.

He recalled how he had met the successful girl band member a week before in the player’s lounge following a 1-1 tie against Chelsea – but she left with friend and fellow Spice Girl Mel C before he was able to get her number.

“I thought, damn, I’ve missed my chance. But then a week later she turned up at Old Trafford. Victoria is not the biggest football fan, as everyone knows. Then Michael walked in with her and I thought I’ll get her number this time!”

During his time at JW3, Beckham took a few moments to help another cause close to his heart – the Make-a-Wish Foundation – and met a group of terminally-ill children, before signing Manchester United and England shirts for them.

Raymond Simonson, CEO of JW3, said:He was simply amazing with them.  He chatted away very authentically, did all the selfies and autographs they wanted, made them laugh and answered their questions. He was a total mensch.”

After the event, both Simonson and Beckham publicly thanked Alan Howard for his support of UNICEF and being the driving force behind the AHF-JW3 Speaker Series, including sponsoring all the tickets on the night to make it free to the public.

The series has now ended for the summer, but former foreign minister David Miliband has been confirmed for November and former prime minister Tony Blair will speak at JW3 next year.