If you're ever feeling listless or lethargic, you could do worse than watch a room of eight- and nine-year-olds on a school trip being suddenly surprised by a certain David Beckham.
Honestly, it should be prescribed on the National Health Service. Their eyes widen to the size of saucers. Their mouths form perfect, cartoonish Os as their brains acknowledge that, yes, one of the most famous men in the world has definitely just walked in to their school day. And then the glee spills out of them. It's both contagious and wonderful.
The worlds of Beckham and the pupils at London's North Harringay Primary School have collided on this overcast October day because he is an ambassador for the Sky Academy.
Set inside the never-ending headquarters of the telecommunications giant, the academy allows school children to learn all about the world of broadcasting and the various jobs involved in it, with 250,000 of them passing through its doors since it opened two years ago. (It also runs sports academies, and offers apprenticeships and work experience placements.)
And this morning, as part of Sky Academy's Confidence Month, Beckham has popped in to watch as North Harringay Primary puts together reports about cyberbullying.
Until the day he passed away, my grandad was unbelievably strict with me, and I want my children to have that, too.
But first, the over-excited eight-year-olds have some questions for him.
"When did you know you wanted to be a footballer?" He was four.
"When did you become famous?" When he was 12 he won a competition to go and train at FC Barcelona for a week. "I thought I was really famous then," he smiles.
"How many goals did you score?""I think about 125," answers Beckham. "Wow! Over 100!" choruses everyone. Later, when we sit down to talk, Beckham tells me he is just relieved that the children recognised him. "I was slightly concerned," he says.
Really? I mean, you're David Beckham ...
"Well, you start realising as you get older that there are some kids who don't know who you are."
Isn't that, well, a little weird for you? "It is a little bit," he says, though I rather suspect it is nice-weird.
Four kids by 40
Beckham is 40 now, but he still has the trademark boyish grin and the years of 24/7 media attention don't seem to have weathered him. He is unfailingly polite to everyone he meets, posing happily for pictures with anyone who asks and apologising to me for a cough he can't seem to shake. "Four kids," he says, by way of explanation.
I suspect that his charming amiability, so rare in the very rich and the very famous, has a lot to do with his transformation from David Beckham, Essex Boy, to David Beckham, Global Mega Star (that and his footballing skills, obviously). You're very, very polite, I say.
"Well, my parents would be so annoyed if I wasn't. It was the way I was brought up. Until the day he passed away, my grandad was unbelievably strict with me, and I want my children to have that, too. From two years old, they have to know their 'pleases' and their 'thank yous' and their 'you're welcomes'. My boys know that they let ladies or girls through the door before they go through the door. It's so important to have manners and treat people from all walks of life the way they should be treated."
His story is a dazzling one of glitz and glamour, but it is also one built on hard work. He retired from football two years ago and could easily afford to put his feet up now, but that isn't his style. It isn't anyone in the Beckham household's style. His wife, Victoria, "works bloody hard", while Brooklyn (whom he refers to, sweetly, as his "16-year-old") works in a coffee shop in west London.
"I remember being 13 and seeing my mum looking after three kids and then still working until 11pm cutting hair," he says. "My dad [a gas fitter] used to go out at 6am and come back at night covered in oil stains from working in the kitchens. They instilled that hard-work ethic into me, and I want to do the same for my children. I could just sit back and watch telly, but I don't want to do that. I still work hard at whatever I do, whether it's taking the rubbish out."
Wait, you take the rubbish out?
"Of course I take the rubbish out!" he laughs. "I work hard at taking the rubbish out and I am very good at taking the rubbish out."
In the name of the father
His father, Ted, was strict and rarely praised him - it was only after he earned his 100th cap that he got a ''well done''. A lesser person might have crumbled, but Beckham saw it as a source of motivation.
In his 22 years as a professional footballer he has had many critics, but none have been tougher than himself. He recalls how, after the notorious World Cup sending off in 1998, he became obsessed with watching back videos of his crosses and free kicks so that he could perfect them.
"That was my way of getting through difficult times of low confidence - hard work." He has spoken in the past about having Obsessive Compulsive Disorder. In watching those videos, was he trying to use it in a positive way, as a sort of coping mechanism? "Oh, without a doubt."
Having watched the North Harringay Primary children make their reports about cyberbullying, I wonder how, as a father, he deals with the endless issues that social networks throw up. "I'm constantly on at my son, who is 16. He doesn't post anything [on Instagram] without showing us [first]. He talks to us about everything, so we are very lucky."
Are his other boys not allowed on social networks? "No. Well, my 13-year-old has a private one because he's allowed to. But, apart from that, no. I think you have to control what your children do to a certain extent."
He says that his kids "don't think about their dad being England captain or playing for United or Real Madrid. They just like playing football. If they don't want to play, I'm not going to get upset about it. As long as they've got an ambition, as long as they're passionate about something, that's all I want for them."
The fame game
I wonder how he feels when children ask him about fame.
"I always say, you know, I didn't play football to be famous. I didn't play football to earn money. I played football because I was passionate about it and it was a hobby for me. I had a 22-year hobby and that is how I have always looked at it. I've been very fortunate to have done what I have done and travelled where I've travelled, and to have what I have. But it's not why I did it."
Now he's ''retired'', he has set up a fund for Unicef called 7 (it's his Manchester United shirt number, as we all know). He donates his own money and raises it, too – next month he is putting his football boots back on for a charity match at Old Trafford that will also feature Zinedine Zidane.
"I've got more time now – well, I say more time – but I've got more time to go out on the ground and really make a difference," he says of his work with Unicef. He plans to take Brooklyn on a trip soon, while Romeo ran in the children's London Marathon this year and raised over £6000 ($12,700) for the charity.
Would you think about running in the big marathon, I ask? "Do you know, as a kid, I always said 'One day I'll run the London Marathon'. But 26 miles is a long way." He laughs. "We'll see. We'll see. Maybe I can get on a bike and ride it."
And if they were going to let anyone do that, then you could bet that it would be David Beckham.
The Daily Telegraph, London