His arm thrown out in the signature ‘lightning bolt’ pose of the fastest man on earth, Usain Bolt, Prince Harry was at his most relaxed as he clowned around with the Olympic champion.

His visit to Jamaica in 2012, where he and the athlete staged a mock race, cemented his reputation as the most personable member of the Royal Family. Here was someone who wore his reputation as the world’s most eligible bachelor easily, and with none of the introspection that so affected his older brother William.

This was the happy-go-lucky Prince, whose popularity was undented — indeed it seemed to be enhanced — by every scrape he found himself in, from falling out of nightclubs the worse for wear to swinging a punch at a paparazzo.

That’s my boy: Harry is cuddled in his mother Princess Diana’s loving arms just short of his third birthday

Even the emergence of pictures of him naked while playing a game of ‘strip billiards’ in a Las Vegas hotel in 2012 did little to damage his image. This was a young man who was neither overwhelmed by royal privilege nor consumed by the responsibilities of royal duty

This image of him walking behind his mother’s coffin between his father Prince Charles and his uncle Earl Spencer, with William and their grandfather Prince Philip, was the most poignant moment of Diana’s funeral

Even the emergence of pictures of him naked while playing a game of ‘strip billiards’ in a Las Vegas hotel in 2012 did little to damage his image.

This was a young man who was neither overwhelmed by royal privilege nor consumed by the responsibilities of royal duty.

So it was nothing short of a seismic shock yesterday to learn, thanks to his candid interview, that behind this playful image, Harry was at this time a deeply troubled young man still struggling to come to terms with the death of his mother, Princess Diana.

Princess Diana with Harry in Majorca in 1987

He had, he confessed, been ‘very close’ to a complete mental breakdown on numerous occasions.

The turmoil over his emotions saw him endure two years of what he described as ‘total chaos’ before seeking professional counselling on the advice of Prince William. He disclosed that he had only begun to address this grief when, at the age of 28, he had felt himself to be ‘on the verge of punching someone’ while also facing anxiety when carrying out official engagements.

Ironically, it was during that period that the Prince was transforming from party-loving playboy to a fully paid up member of the royal ‘firm’.

As someone who has watched Harry from nursery school toddler to accomplished soldier and much-loved Prince, his frank admission revealing how he has coped — or rather not coped — since his mother’s death in Paris in 1997, is startling.

His words are shatteringly honest. ‘I can safely say that losing my mum at the age of 12, and therefore shutting down all my emotions for the past 20 years, has had a quite serious effect on not only my personal life, but my work as well,’ he said.

Yet how well he has bottled up all this sorrow over the past two decades. Only those closest to him have ever known the extent of the anguish he carried inside.

A pivotal figure in his life was former royal nanny Tiggy Legge-Bourke, who was especially close to Harry. They are pictured here together in 1999

Harry pictured at his passing out parade at Sandhurst with Tiggy in April 2006. Tiggy was key in the first two years after Diana’s death and until after Harry was at Eton College

That image of him walking behind his mother’s coffin between his father Prince Charles and his uncle Earl Spencer, with William and their grandfather Prince Philip, was the most poignant moment of Diana’s funeral.

All the advantages of his privileged birth were cruelly counterbalanced by the disadvantages of losing his mother just two weeks short of his 13th birthday.

For any young child, losing a parent is profoundly shocking. When that parent is the most famous woman on the planet, the distress must be endless.

Because for Harry, there was never any danger of his mother being too easily forgotten. Far from it, Diana was simply too big a figure for that. Her influence, not just on William and Harry, but on the whole of the Royal Family, has simply never gone away.

Two days before the Princess’s funeral, the brothers went with their father to see the lake of flowers placed in tribute to their mother at Kensington Palace and then went inside to the apartment where they had lived. Instantly, Harry burst into tears and fell into the arms of Diana’s butler, Paul Burrell. The boy was inconsolable.

For two years afterwards, Harry would weep for his mother. He was still tearful about her absence during a family summer holiday aboard the late Greek shipping tycoon John Latsis’s yacht, Alexander, in August 1999.

So how did his father and other members of the Royal Family help Harry come to terms with his loss?

Certainly, the way in which the Prince of Wales set aside his own unhappy experiences of his life with Diana, and filled Highgrove, his Gloucestershire home, with photographs and mementoes of the marriage, helped.

‘He arranged to have lots of framed pictures of the Princess dotted around the house,’ recalls an aide. ‘Despite his own personal feelings, he knew that Diana had been a brilliant mother, and he wanted to ensure there were plenty of reminders of her that the boys could see every day.

‘Old wedding presents were dusted off, anything for which there could be a common talking point.’

Prince Harry with his mother enjoying the rides at Thorpe Park in August, 1997

Earl Spencer, Prince William, Prince Harry and Prince Charles look at the coffin of Diana, Princess of Wales, during her funeral in London in September 1997

It was an act all the more extraordinary when you consider that, not long before, as the couple were divorcing, Charles did all he could to eradicate Diana’s memory by redecorating the house.

Charles also encouraged his sons to talk about their mother around the dining table, for example, and asked his friends to share their memories of her with them. This cannot have been easy, for many of these friends had sided with the Prince when the royal marriage was breaking up.

In the very masculine atmosphere of Highgrove and St James’s Palace, where Charles then had his office, there were few female role models on his father’s staff whom Harry could confide in, should he have wished to. Two who did help him were former Press secretary Sandy Henney and her successor Colleen Harris. Both provided a shoulder for him to lean on.

The pivotal figure at this time, however, was former royal nanny Tiggy Legge-Bourke, who was especially close to Harry. The Prince is godfather to her elder son Fred, now 15 — younger son Tom has William as a godparent.

Tiggy was key in the first two years after Diana’s death and until after Harry was at Eton College. Unlike William, who flourished at the school, Harry was less successful there, making fewer friends and finding the work hard.

Had he got his way, it is quite possible that he would have gone somewhere less academic, but Charles was convinced he needed to be close to his brother.

By the time Harry was 16, it was clear that all this mentoring was not necessarily working.

Eton scholar: Unlike William, who flourished at the school, Harry was less successful, making fewer friends and finding the work hard

Charles encouraged his sons to talk about their mother around the dining table and asked his friends to share their memories of her with them

It emerged that during a two-month period when William was away on his gap year and Charles was distant and busy with royal engagements — and his romance with Camilla Parker Bowles — Harry was often to be found in country pubs near Highgrove, where he was exposed to a dangerous cocktail of underage drinking and the illegal drug cannabis.

Looking back now, it is clear this must have been a critical moment. He missed his mother terribly, his father and brother were not always around — and he was easily led astray.

If ever there was a moment for his mother’s family, the Spencers, to become involved, it was then. At her funeral, Diana’s brother Lord Spencer had famously, and very publicly, pledged to play his part in William and Harry’s upbringing.

Perhaps the only certainty in Harry’s decision to speak out is that he is very much his mother’s son

But the fact is his contact had been minimal, not least because with a young family then based in South Africa, Spencer simply was not around enough.

In truth, Harry was closer to Diana’s sisters, Sarah and Jane, and their children.

The cousins had often holidayed together and those bonds remained. Lady Sarah, for example, made sure that Harry received the 13th birthday present Diana had intended him to have, and tried to attend sporting fixtures when he was still at Ludgrove prep school in Berkshire.

One is entitled to wonder what part, if any, the Princess’s friends played. The answer, sadly, is not very much.

Several of her close friends wrote to the boys offering to share their memories of Diana, only to receive a brush off from an aide.

One told me: ‘One can’t blame the boys, they were only young, but the only conclusion you are left with is that the people around them didn’t really want us involved. Perhaps it was all too uncomfortable.’

Another said: ‘Rightly or wrongly the Royal Family seem to typify the stiff-upper-lip approach, but Diana was not like that and it now seems that Harry isn’t either.’

As the world knows, for the past nine months Harry has been dating Californian-born actress Meghan Markle whose own mother, intriguingly, is a therapist

Prince William and Prince Harry bowing their heads as their mother's coffin is taken out of Westminster Abbey following her funeral service

Over the 20 years since her death, Diana’s reputation has suffered damage; revisionist writers have denigrated her memory while there have been few to champion her.

It was against this backdrop that Harry tried to ignore his grief. As he put it in the interview: ‘My way of dealing with it was sticking my head in the sand refusing to ever think about my mum, because why would that help? It’s only going to make you sad, it’s not going to bring her back.’

According to Harry’s timescale, his years of turmoil occurred towards the end of his 20s, and yet it was in the early part of that decade that he was attracting the wrong kind of attention. In 2004, he got into an altercation with paparazzi after a scuffle outside a London nightclub. That incident takes on more significance now in light of his comments about his suppressed emotions and his desire to ‘punch’ someone.

Boxing, he said, provided an outlet for his frustration. (This, presumably, was when he was still in the Army and able to use a gym away from prying eyes.)

The following year he had to issue an apology after being photographed wearing a swastika armband to a fancy dress party.

Aged 26, he was reported to have been seen taking ‘hippy crack’ (nitrous oxide or laughing gas) from filled balloons being sold at £1.50 a time.

And then, of course, there were his Las Vegas frolics which he later admitted had let himself and his family down.

All this, of course, could be filed neatly under the heading of youthful indiscretion. After all, many a young man eager to kick over the traces has done far worse than Harry.

So a clue, perhaps, lies in his remark that shutting away his emotions has played havoc with his personal life.

During the period of turmoil Harry appears to be talking about, he had two significant romances, one with Zimbabwe-born Chelsy Davy, and the other with actress Cressida Bonas.

He did not mention either girlfriend in the interview, but was widely reported to have been in love with both of them.

The relationships ended because neither woman felt they could adjust to the extraordinary pressures of being a royal wife.

Was he blaming himself for the failure of these romances? It certainly seems so.

His mother's son: Harry jokes around with three-year-old orphan Lerato during a visit to Phelisanong Children's Home in Maseru, Lesoth

As the world knows, for the past nine months Harry has been dating Californian-born actress Meghan Markle whose own mother, intriguingly, is a therapist.

One theory doing the rounds in royal circles last night is that this connection might have been behind Harry’s decision to speak so honestly, and movingly, about his life and problems.

Such openness among the royals is rarely seen. Earlier this month, biographer Sally Bedell Smith claimed in a new a book about the Prince of Wales that Diana’s emotional instability sent Charles into therapy for 14 years. If so, the Prince of Wales has said nothing about it.

Princess Diana did talk about her battles with bulimia, the eating disorder which cast such a shadow over her marriage. She also consulted psychotherapist Susie Orbach and took up kickboxing as a way of dealing with her anger.

Perhaps the only certainty in Harry’s decision to speak out is that he is very much his mother’s son.