Is this the most touching picture of Prince Philip ever taken? On the anniversary of Kennedy's assassination, we look back at the  Royal Family's friendship with the president - and the care they showed for John Jnr, the child left without a father...

It’s one of the most touching photographs of Prince Philip ever taken. 

He is holding the hand of a four-year-old boy in a white coat, looking down at him with evident concern, while the boy’s mother looks across at the Duke, her eyes conveying her thanks.

The mother is of course Jacqueline Kennedy, widow of John Fitzgerald Kennedy, 35th President of the USA, who had been cruelly slain by an assassin’s bullet just 18 months earlier.

The four-and-a-half-year-old boy is their son, John Jnr, who had already touched Philip’s heart when the two met at the White House on the day of JFK’s funeral.

News of Kennedy’s death on 22 November 1963 shocked the world. The Queen and Duke as well as the Queen Mother sent messages of condolences to Jackie and plans were hastily drawn up for representatives from Britain to attend the funeral which was scheduled for just three days later.

At the time of the assassination the Queen was pregnant with Prince Edward, so Philip represented her at the ceremony in Washington.

He flew from London with the Prime Minister, Alec Douglas-Home and his wife, the Leader of the Opposition, Harold Wilson and the Duke and Duchess of Devonshire (Andrew Devonshire's older brother had married JFK's sister Kathleen.)

Deborah Devonshire later recalled Philip inviting her to join him for dinner with Wilson during the flight, with the other guests on an adjoining table. The two men 'started talking about aeroplanes in such an incredible, technical way that it was quite impossible to listen to them and I found my mind wandering.'

Given that there was such little time to prepare for Kennedy's funeral, it was, in the Duchess's words: ‘not surprisingly, rather chaotic.’

When Philip arrived at St Matthew's Cathedral, he found he hadn't been allocated a seat and the Douglas-Homes had to move further back to make room for him. 

On the cathedral steps after the service 'Debo' noted 'Prince Philip's stern blue look' as he struggled to contain his emotion.

Others openly wept as the president's son John Jnr three years old that day, saluted his father's coffin as it passed by to the presidential anthem 'Hail to the Chief.' Inside the cathedral earlier there had been more tears when 'John-John', whose third birthday fell that day, called out 'Where's my Daddy?' and 'Somebody pick me up'.

Access for the prince at JFK’s internment at Arlington Ceremony was no better. The Duchess noted he 'was jostled at the back again and behind a lot of soldiers, so he was not among the foreign visitors when they came away from the grave.’

The prince was accorded one special tribute by Jackie herself. At the White House later in the day a large reception was held for the 220 representatives, from 92 countries – thought to have been the largest collection of dignitaries at the passing of a head of state since the funeral of Britain's Edward VII in 1910.

While members of the Kennedy family hosted the event in the State Dining Room, Jackie held a more intimate gathering in the Oval Office where she had requested Philip, President de Gaulle of France, Ethiopia's Emperor Haile Selassie, and Ireland's President Éamon de Valera should join her for tea.

Leaving the reception Philip was amused to see 'John-John,' in full birthday party mode, running down the corridor hotly pursued by his flustered nanny.

'The kind-looking man watched me catch him,' Maud Shaw later recalled, ‘” I’ve got one like that,” he grinned, referring to Prince Andrew. “They're a handful, aren't they?” At this point he squatted down on the floor to play with the toddler.' 

Meanwhile in the Oval Office, Jackie and her brother-in-law Robert Kennedy were talking to de Valera about Jack’s visit to his ancestral home in Ireland just five months earlier.

During the visit the president had been greatly moved by a poem written by the first lady, Sinéad de Valera, an accomplished folklorist, and poet.

The memory caused Bobby Kennedy to release the pent-up anguish of the previous few days in a flood of tears, prompting both de Valera and Jackie to break down as well.

As Jackie left to compose herself, still in tears, she opened the door into the corridor where Philip still lay sprawled on the floor with her son.

Seeing her distress, the Duke jumped up and, red faced with embarrassment at the awkward moment, explained how her young son reminded him of his own three-year-old and that he couldn’t resist talking to him.

As the little boy stared up at the adults, Jackie asked him: 'John did you make your bow to the prince?' at which point her son announced forcefully 'I did,' which helped to diffuse the tension.

Philip rejoined Jackie in the Oval Office where, to help them unwind, the young widow and her sister Lee Radziwill sipped Bloody Mary’s.

Philip had met Lee a couple of years earlier at a Buckingham Palace banquet for the US President and First Lady. That evening ended with the Queen, mindful of Jackie's interest in all things equestrian, walking her through the Picture Gallery, halting at a van Dyck portrait of Charles I on horseback, before declaring 'that's a good horse!'

Lee later recalled being escorted on the gallery tour by Philip who joked: 'You're just like me – you have to walk three steps behind.'

After the palace banquet Jackie told the writer Gore Vidal that she thought Philip 'nice but nervous.' Now in the Oval Office, she found him a reassuring presence.

As the two sisters chatted to the Duke the White House Chief of Protocol approached Jackie and suggested she should meet the other VIPs downstairs.

According to William Manchester who wrote the official account of the Kennedy assassination and its aftermath, after being asked if she wanted to mix informally with the guests or receive them in a line-up ‘she looked at Philip appealingly.’

The ever-practical prince came to her rescue, telling her 'I’d advise you, you know, to have the line. It’s really quicker and it gets it done.' 

As she left her royal guest Jackie remembered protocol and dropped Philip a perfect curtsey, remarking to an aide: 'I’m no longer the wife of the chief of state.'

The bond between Philip, Jackie, and the fatherless little boy he had played with at the White House was very clear that sunny Friday afternoon at Runnymede as they stood in a line to see the stone memorial honouring the president who died in his prime.

At the unveiling the Queen praised John F Kennedy, telling Jackie and her children: 'with all our hearts, my people shared his triumphs, grieved at his reverses and wept at his death.'

• Ian Lloyd is author of The Duke: 100 Chapters in the Life of Prince Philip. The History Press