Not many fathers have a fluorescent-blue Superman T-shirt lurking in their wardrobe. But Matt O'Connor is not like many fathers. Dressed in the offending item, which peeks out from beneath a rather incongruous beige raincoat, he has come to talk fatherhood, with the two sons from his previous marriage, Daniel, 12, and Alex, 10, in tow. (He now also has a third son with his new partner Nadine.)
O'Connor is the man behind the paternal rights group Fathers4Justice and he has made embarrassing his children a daily pastime since he set up the organisation in 2002. The 41-year-old has masterminded an array of high-profile stunts, from hitting Tony Blair with condoms full of flour during Prime Minister's Questions, to dressing as Father Ted and gate-crashing a church meeting.
We meet – rather appropriately – outside Buckingham Palace, where, four years ago, O'Connor organised his group's biggest stunt yet: getting two fathers dressed as Batman and Robin to scale the perimeter fence and climb on to the roof of the palace. While dressing up as superheroes and ascending high buildings has been a signature of the charity, the O'Connor kids have been spared that particular embarrassment. Not only is O'Connor scared of heights – a subject of much hilarity for his boys – he's also not a big fan of the costumes. "I'm more Michelin Man than Superman," he chuckles.
But that hasn't stopped him dabbling in the dressing-up box. In 2003, he donned a jumpsuit to perform "Heartbreak Hotel" as Elvis along with around 50 other dads outside the Royal Courts of Justice.
"It wasn't the right look for me," he admits, "It was more like Elvis just before he died – jumpsuits really aren't my thing." There are nods of abashed agreement from the boys.
Wearing clothes he describes as "so loud you can see them on Google Earth", O'Connor is a born exhibitionist and his son Alex looks like he has inherited more than the cheeky grin. Today he is wearing a T-shirt emblazoned with "I blame the parents" and he likes it when his dad ends up on TV.
"At school people talk about it," he says. "They say, 'I saw your dad on the news,' and I think, 'Ooh, that's cool.'" His older brother is less convinced. Just approaching his teenage years, Daniel is the most thoughtful of the three and you get the feeling he'd quite like it if his father gave the loud shirts and telly stunts a miss.
It is sometimes hard for O'Connor to separate his enthusiasm for the cause of fatherhood from that of furthering his own profile. Last month he stood as a mayoral candidate for London, which was yet another source of mirth for his boys, as he forgot to remove his earrings for the party political broadcast. "He looked like something out of Pirates of the Caribbean," laughs Alex.
But just as certain as O'Connor's desire to be in the public eye is his affection for his sons. "People often say to me that I'm in this for some ulterior motive, that I'm in it for the money or whatever. But I've got my own business – I'm a successful businessperson. My motivation is sitting beside me now," he says, nodding towards the boys.
It may be a neat turn of phrase but it also appears to be true. And his desperation for his sons' approval is palpable.
When asking what they'd do if they were dads and couldn't see their kids, he says, almost pleading, "You'd do what I did, wouldn't you boys?" Daniel seems reticent. "If I ever had kids I would probably fight [for the right to see them], yeah," he says. "But I wouldn't wear the costumes, I'm not that mad. I'd do it in a more social way. I understood what you were trying to do..."
He trails off, seemingly bemused by his dad's methods. Was Daniel pleased that his father did the stunts? "Urr, half and half, I guess," he shrugs. "I think your plans are a bit unusual, Dad," he adds. And then his mood lifts and he gives his dad an affectionate punch on the arm, saying, "I am glad that we're seeing you though."
Almost as often as Daniel and Alex get embarrassed by their dad, they are showing him up themselves. "Whenever he embarrasses us, we bring up the London Eye," says Daniel, referring to his father's pathological fear of heights. "Yeah, he pooed his pants up there," squeals Alex.
When O'Connor began Fathers4Justice the embarrassing stunts had an urgent purpose. He had broken up with his former wife Sophie and was going through the court system to gain access to his children. It was a tough time but he says things are "fine now" – although their mother has little patience with his stunts. "I don't think your mum's a huge fan of my antics," he confesses to his sons and the boys nod their agreement.
"She knows you too well," says Daniel.
"I can't blame her," O'Connor continues. "Having an embarrassing ex-husband is not exactly what you want. You'd rather have an ex that just quietly melted into the background somewhere, never to be seen again.
"I think their mum found it difficult at one point because she had parents coming up to her, saying, 'Why is he doing that – he's seeing the boys isn't he?' And perhaps she has a point." Though initially his ex-wife sought to create distance between him and the boys, after a year they had resolved their differences and he was able to meet them freely. So why does he keep up the crusade?
He isn't just in it for himself, he says. He is fighting for other fathers who have been barred from their children. In fact, he is already planning his next step as we speak. "I've seen a gap in the perimeter fence today," he says, conspiratorially, glancing up at Buckingham Palace. "They increased the security after we went in but I've seen a chink."
'Fathers 4 Justice: The Inside Story' by Matt O'Connor (Orion, £18.99) is out now
Men in tights: The real dads' army
Founded in 2002, Fathers4Justice campaigns for a more open and equitable system of family law. Its protests often involve superhero costumes as, in their words, "Fathers have the role of superhero in the lives of children." Among its higher-profile stunts are:
Batman on Buckingham Palace
In 2004 Jason Hatch narrowly escaped being shot by police marksmen when he scaled a wall at the Queen's place dressed as Bruce Wayne's alter ego. Luckily, police made a "split-second decision" that a man in tights was unlikely to be a threat.
The 'Fun Powder' plot
Ron Davis and Guy Harrison were arrested, also in 2004, after hurling condoms filled with purple powder at Tony Blair in the House of Commons.
Angry at David Cameron's comments that absent fathers were partly responsible for a rise in antisocial behaviour, three Fathers4Justice members last year scaled Stonehenge dressed as Fred Flintstone with a banner reading: "Drag the family courts out of the Stone Age".