Intimate details have emerged in a new documentary to air in the UK tomorrow evening, Tuesday, December 21, of how the late Duke of Edinburgh “secretly” comforted Prince William at Diana’s funeral in 1997, when he thought the cameras couldn’t see them.

Viewers of the ITV documentary, ‘Philip: Prince, Husband, Father’, will hear how Prince Philip “gently touched William on the back to comfort him” in an “awful, awful moment” when he thought they were “out of shot of the cameras”.

The moving account, which reveals a hidden softer side to the Queen’s consort, comes from Martin Palmer, who co-founded The Alliance of Religions and Conservation with Prince Philip. Palmer says in the documentary that the late Duke personally relayed the anecdote to him.

“He knew what it was like to be a member of a dysfunctional family and he did his damnedest to make sure that did not happen to his grandchildren,” Palmer reveals in the programme, according to The Telegraph.

“You’ve just got to watch that moment and realise here is a grandfather who is trying to help his young, very vulnerable grandson struggle through this awful, awful moment.”

The funeral footage will be aired as part of the televised tribute to the Duke, who died in April, aged 99, and will show a number of royal experts and associates of Prince Philip sharing their memories about him; as well as revisiting some of his own characteristic words over the years.

According to the ITV press promo: “The film puts Prince Philip’s own words front and centre, drawing on rare archive and audio recordings spanning 80 years, to let us hear Prince Philip talk – with his characteristic humour and forthright tone – about the role of the monarchy, press intrusion, Prince Charles’ future… topics that are hugely relevant today and which show the different sides of Philip: Prince, husband and father.”

In the programme, Palmer adds that contrary to popular opinion, it was not Prince Philip’s idea for the two young princes, who were aged 15 and 12 at the time, to walk behind their mother’s coffin.

“He’s come in for criticism for that but it was not his choice, not his idea. And there’s a moment where they go under the Horseguards Parade arch where it’s quite clear that Prince Philip – and I asked him about this he said, ‘Yes, I didn’t think the cameras could see us’ – at that point he turns to William and comforts him.”

Meanwhile, the Duke’s biographer, Gyles Brandreth, tells the documentary that Prince Philip had not been meant to take part in the funeral walk, but did so “as an act of grandfatherly kindness”.

“There was no plan originally for Prince Philip to be part of that,” says Brandreth on the show. “Prince Philip said to Prince William, ‘If it would help I can walk alongside you.’ So far from being what was reported, it was an act of grandfatherly kindness.”

‘Philip: Prince, Husband, Father’ will also include colourised footage of the Queen and Duke in their younger years as happy newlyweds.