Swept up in the euphoria of Aston Villa’s Europa League triumph in Istanbul last week, the Prince of Wales shouted, cried and hugged fellow football fans as if he was just another one of them.

Here was the future King, surrounded by his mates, singing out his heart like any other die-hard supporter. Tellingly, he looked happier and more relaxed than he has in years.

So what does this blokeish glimpse of William tell us about the man behind the royal titles?

And, crucially, what does last week’s spontaneous outpouring of emotion reveal about the underlying tension between the Prince’s desire for a normal life with family and friends amid his burgeoning duties as heir to the throne?

As a royal source exclusively told the Daily Mail this week: ‘He’s a 40-something bloke, well off, with a happy family, but all that currently waits for him is a metaphorical straitjacket and a very heavy crown.’

At 43, and saddled with a predestined royal role as monarch in the wings, William is said to increasingly treasure his ‘life with the lads’.

The ‘boys’ football trip’ to Turkey was arranged just a matter of weeks ago.

Those who were with William in Istanbul last Wednesday include long-term pals Thomas van Straubenzee and Edward van Cutsem and his 17-year-old son Jake. William has known 43-year-old Thomas, a senior executive at upmarket estate agency Knight Frank and godfather to Princess Charlotte, since they were small boys studying together at Ludgrove Prep School.

Former banker Edward, 52, who was seen joking around with William and even patting him roughly on the head, is one of the King’s godsons and was a page boy at his 1981 wedding to the then Lady Diana.

Also on the terrace was 45-year-old Ben Dawes – known to William as Dawesey – whose late father once ran a legendary greasy spoon and biker cafe called Dinky’s Dinahs from a lay-by off the A458 near Shrewsbury.

Dawes runs a wine delivery business with his wife Pip and lives in Merton Park near Wimbledon in south-west London. Unlike most of William’s wealthy circle, the couple sent their two children to a local state school.

‘Their meetings are infrequent but cherished,’ adds the royal source. ‘The lads are particular fans of barbecues, beer and a lot of wine.’

Indeed William’s band of brothers prefer to gather at each other’s houses well away from the gaze of the public or, failing that, to meet at pubs in West London with discreet landlords and quiet back rooms, where the Prince is said to be partial to a pint of Stella Artois.

They usually holiday abroad together at least once a year – often at a ski resort.

William, according to the source, ‘dons an occasional disguise’, either growing – or shaving off – a beard, wearing a hat and glasses and, on occasions, employing an ‘iffy’ Welsh accent to put strangers off the scent. During these precious off-duty moments, conversations about William’s current or future roles are strictly off limits and generally revolve around family, their children, jobs and sport.

‘Like all senior royals, he rarely lets his guard down with anyone,’ says the source. ‘He is wary of getting too close to others. His true inner circle is very select. They have no axes to grind and know how to behave.

‘Their occasionally boisterous behaviour has to be toned down so as not to draw too much attention to themselves but these are sort of “let your hair down” moments for William who can’t act like this anywhere else.’

More, in a moment, of the growing divergence between the Prince’s private and public life, not to mention the occasional clash with his father over their very different views of how the monarchy should evolve.

For William’s jaunt to Turkey comes amid growing concern in royal and government circles about his apparent reluctance to travel abroad for official duties unless it’s for something which interests him personally. He is said to have been ordered to attend the funeral of Pope Francis by King Charles last year after avoiding the funeral of former US President Jimmy Carter.

Most recently, as the Daily Mail’s Ephraim Hardcastle revealed earlier this month, he is said to have declined the idea of a trip to Jamaica six months after the island nation was devastated by Hurricane Melissa.

His apparent lack of interest in Commonwealth countries has also been noted.

’It’s been a particular source of concern to the Foreign Office who have struggled to get him on a plane to spread some royal limelight,’ says the royal source. ‘The big overseas trips have been exclusively to do with his Earthshot Prize but he has made eight visits to watch rugby or football.’

The Prince’s desire for a life away from the confines of royal palaces was shaped early on – both by Princess Diana, who on occasions made him and his brother Harry join queues and use cash, but most of all by his wife’s family and his visits to their home in the Berkshire village of Bucklebury.

‘William found the informality eye-opening,’ says the royal source, who explains that the Prince took close note of how Carole or Kate would get up from the table to check on food in the oven or add the finishing touches to dessert before serving it themselves.

Aside from learning how to load a dishwasher, an early challenge faced by the Prince came when he was asked to set the table for Christmas lunch. ‘Laying a tablecloth was a struggle and placing the cutlery embarrassing. He tried to claim it was because he’s left-handed,’ says the royal source.

‘That the Middletons had to nip to the shop for food, ensure there was enough bread in the house, empty their own bins and put out the recycling on the right day were all refreshing.’

These experiences also helped him when he and Kate set up their first home together in a rented cottage on the rural island of Anglesey where they lived for three years while William worked as an RAF search-and-rescue helicopter pilot and where the couple were frequently spotted shopping for groceries at a branch of Waitrose in nearby Menai Bridge.

‘His first experience of a big shop following Carole’s detailed lists was apparently mind-boggling,’ says the source. If this foray into rural domesticity was seen by the Palace as a short reprieve before the onslaught of roles as full-time royals, then it is clear that it also gave the couple a keen sense of the kind of environment in which they wanted to raise their future children.

At Anmer Hall, the Prince and Princess of Wales’ much-loved country estate in Norfolk, his closest pal is the 7th Marquess of Cholmondeley, who lives next door on the historic Houghton Hall estate, but their friendship – and that shared by their wives – is anything but stiff and starchy, even though there is a significant age gap between the Marquess, who is 65, and the Prince.

The Marquess, who served as Great Lord Chamberlain to Queen Elizabeth II and is a permanent Lord-in-Waiting to the King is known as ‘Rocky’ to Prince William. He and Kate form a regular foursome with Rocky and 42-year-old Rose, cooking supper for each other, hosting dinner parties and attending the occasional local Norfolk charity event.

This week, a former friend of Rose’s from Stowe School told me that she is ‘wonderfully down-to-earth’ and, like the Prince and Princess of Wales, relishes life with her husband and three children in the country.

The royal source adds: ‘They keep all of it very low key and try to have as normal a life as possible despite the grand backdrops.’

But where does all this fit in with William’s royal duties and, how will life with his inner circle be impacted when, one day, he assumes the throne?

Royal life, according to the source, ‘is the one William finds the hardest’, particularly the pre-set diaries and annual routines.

He landed himself in hot water with the late Queen nine years ago when he skipped the annual Commonwealth Day service at Westminster Abbey to go skiing with ‘the lads’ in Verbier, Switzerland, and was subsequently filmed ‘dad dancing’ in a nightclub, footage of which went viral and earned him a written rebuke from Her Majesty.

Van Straubenzee also accompanied him on that trip, as did Guy Pelly, 44, who has been a close friend since the early 2000s when he co-founded upmarket London clubs such as Mahiki and Whisky Mist, where William and Kate used to party with friends.

William is said to find the rigid formality of his father’s households ‘stifling’, largely due to the fact that staff are a constant presence and true privacy is impossible.

According to the Daily Mail’s royal source: ‘He has introduced a lot of relative informality into home life – notably there are fewer flunkeys wandering around [his and Kate’s homes].’

While George, Charlotte and Louis’ nanny and her assistant are close to the family, a valet and housekeeper largely operate out of sight.

At both Kensington Palace in London, where the Wales’ still have apartment 1A, and Anmer Hall, it is understood that the couple’s private secretary and office staff are not allowed to roam around as might normally be found in a royal household.

When in residence at their main family home, Forest Lodge, office staff are housed separately at nearby Windsor Castle.

‘The cook is sometimes redundant as William or Kate often cook themselves,’ says the source.

And, of course, what William revealed about himself in Istanbul last week was how much he values his small coterie of friends. ‘One thing is certain, he won’t be abandoning his inner circle when he takes the crown,’ says the source.

If he is said to mistrust the ‘grey suits’ at the Palace, then he didn’t hesitate when it came to letting down his guard with a bunch of football fans.

It was, as he pointed out in a rare, emotional message posted on social media straight after Villa’s win against German side Freiburg, ‘an amazing night’ and ‘44 years since the last taste of European silverware’.

He was referring to his team’s 1982 victory against Bayern Munich in what was the European Cup, and is now the UEFA Champions League – which came just 26 days before his birth.

If he and his fellow Villa fans waited nearly half a century to experience the same joyful triumph, then those decades have also seen William grow from a shy child into an earnest teenager and, now, a husband and father-of-three with a strong mind of his own.

One, who no doubt hopes his beloved Villa wins a European trophy again before he himself is the one obliged to wear the crown.