The Duke of Sussex’s decision to rush to the King’s side following his cancer diagnosis is testament to the bonds that remain between the two men.

Their relationship was severely strained following Harry’s decision to step down as a working royal in 2020 and air a catalogue of grievances against the institution of the monarchy and members of his family in a series of interviews.

He was left barely on speaking terms with his two closest relatives – Charles and the Prince of Wales.

Harry’s controversial memoir Spare further damaged his ties with his father and brother, making claims William physically attacked him, the King put his own interests above Harry’s and was jealous of the Duchess of Sussex.

In a television interview to promote the book when published last January, the duke revealed the state of his relationship with Charles and William, saying he was currently “not texting” his brother and at the time had not spoken to his father for “quite a while”.

Harry was last seen with members of the monarchy when he visited the UK to attend the King’s coronation in May last year without Meghan, and reportedly flew home to California within hours of the ceremony ending.

Charles’s health scare has brought his son back to the UK, and where there is contact there is the possibility of a reconciliation between father and son – but Harry and William remain estranged.

It is understood the Prince of Wales has no plans to meet his brother during his brief visit.

The obstacles to surmount remain significant for father and son – in his 2021 interview with Oprah Winfrey, Harry said Charles stopped taking his calls when he was trying to discuss stepping down as a working royal in 2019.

He added: “My father and my brother, they are trapped. They don’t get to leave. And I have huge compassion for that.”

Harry’s most damning comment was that a senior member of the royal family – not Queen Elizabeth or the late Duke of Edinburgh – allegedly voiced “concerns” about the skin colour of the Sussexes’ son Prince Archie before he was born.

In a series of interviews to promote his book, Harry attacked the reputation of Charles’ wife Queen Camilla, saying her willingness to forge relationships with the British press made her “dangerous” and criticised her attempts to rehabilitate her “image” at his cost.

Just weeks after Spare was released, Harry and Meghan were asked to “vacate” their UK home, Frogmore cottage close to Windsor Castle, with reports claiming the move was sanctioned by the King.

But later that year Harry reportedly phoned his father on his 75th birthday last November to wish him well.

The warring royal brothers may yet take to heart the words of Charles who, according to Harry’s memoir Spare, told them after their grandfather the Duke of Edinburgh’s funeral “Please, boys – don’t make my final years a misery”.