The Queen and other senior royals refused to applaud after Lord Spencer delivered his vitriolic eulogy at Princess Diana's funeral, even though her sons, Princes William and Harry, did.
In a gripping new ITV documentary, Diana: The Day Britain Cried, which reveals for the first time the inside story behind the day the royal was laid to rest, one of the Queen's most senior courtiers opens up about the thinly-veiled attack made by her brother on the Royal Family.
One member of the congregation also describes the 'peculiar and unusual' moment the applause and cheers that greeted his controversial eulogy outside Westminster Abbey rippled through the congregation, which had been listening in stunned silence.
It is not clear whether the princess's sons, who were 15 and 12 when she died and clearly beset by grief, understood the full extent of what their uncle was saying.
But the awkwardness of the moment is encapsulated by Martin Neary, the Abbey's musical director, who says: 'I felt a great sympathy for what she had suffered but at the same time I was shocked by some of things which were said.
'The princes actually applauded at the end, although the senior members of the Royal Family did not.'
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Following Earl Spencer's controversial euology at Diana's funeral, senior royals did not join in the applause although her sons William and Harry did, according to a new documentary
The Queen and Prince Philip did not applaud Earl Spencer's speech, which seemed to be a thinly-veiled attack on the royal family at her funeral
Speaking for the first time, like many of the participants, Sir Malcom Ross, one of the Queen's right-hand men who was responsible for the funeral arrangement, adds: 'It grated to me on the day because I thought he was actually having a little bit of a go at the Royal Family.
'It was my mistake to leave the doors of the Abbey open. What that meant was that when Lord Spencer made his remarks the audience outside applauded, which, in fact, started the audience inside applauding.'
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He adds, rather unconvincingly: 'Fine. I don't think anybody took offence.'
In his address a clearly furious Earl Spencer made a public pledge that 'we, your blood family, will do all we can to continue the imaginative way in which you were steering these two exceptional young men so that their souls are not simply immersed by duty and tradition but can sing openly as you planned.'
EARL SPENCER'S SPEECH THAT SHOCKED THE ROYALS
She would want us today to pledge ourselves to protecting her beloved boys William and Harry from a similar fate and I do this here Diana on your behalf. We will not allow them to suffer the anguish that used regularly to drive you to tearful despair.
'And beyond that, on behalf of your mother and sisters, I pledge that we, your blood family, will do all we can to continue the imaginative way in which you were steering these two exceptional young men so that their souls are not simply immersed by duty and tradition but can sing openly as you planned.
'We fully respect the heritage into which they have both been born and will always respect and encourage them in their royal role but we, like you, recognise the need for them to experience as many different aspects of life as possible to arm them spiritually and emotionally for the years ahead. I know you would have expected nothing less from us.
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Sir Malcom Ross is the most senior member of the Royal Household ever to speak about Diana's death and features extensively in the new ITV documentary, narrated by actress Kate Winslet, Diana: The Day Britain Cried.
Made by Finestripe Productions to mark the 20th anniversary of her death, and with the knowledge of William and Harry, its executive producer, Sue Summers, describes the funeral as the 'great untold story of her death'.
Sir Malcolm admits that when Diana died, in a car crash in Paris on August 31 1997, there was no plan in place for her funeral.
Sir Malcolm Ross Senior Official in the Royal Household said that the eulogy seemed like Earl Spencer was 'having a little bit of a go at the royals' but insisted nobody took offence
'I had plans for all the members of the Royal Family of a certain age so that I would be ready. But of course in this instance, I wasn't ready,' he says.
'Nobody at that stage knew whether it should be a Spencer family funeral or whether it was going to be a royal funeral. Princess Diana was no longer a member of the Royal Family, she had left the fold.'
Asked about the Queen's much-criticised decision to stay with her grand-children in Scotland until just before her former daughter-in-law was laid to rest, he adds: 'The Queen had decided she would stay in Balmoral, particularly to look after her grandchildren.
'It was the Queen's decision to keep her grandchildren safe and out of the public eye.'
The Duke of Edinburgh, Prince William, Earl Spencer, Prince Harry and Prince Charles following Diana's coffin to Westminster Abbey
With just five days to organise it, Diana's funeral was an enormous undertaking not just in terms of who to invite – but how to get those 2,000 individual invites to them.
He reveals for the first time how the head of the Post Office held up the entire day's First Class post for an hour on Thursday, September so that he could get the invitations out and brought in 1,200 extra staff to help deliver them.
He said: 'An enormous number of people wanted to come and, dare I say it, an enormous number of people thought they should come. And somehow we had to siphon that down to the people who really should come.
'So we got into the Princess's world, looking at her Christmas card list, talking to her really special near friends.
The Queen, pictured leaving the service with her husband and mother, had faced public criticism for staying away from London in the run up to the funeral
'It had always been my plan to get everything relating to attending the service into the First Class post on Thursday evening. So it was a scramble.
'I telephoned the person who ran the Post Office who he said that he would hold the First Class post for one hour. What he didn't tell me was that he called in twelve hundred postmen who drove their vans from all over Britain to collect the invitations. Everyone had theirs by midday [on Friday]. '
Eight Welsh Guards, led by chief pallbearer, Captain Richard Williams, were selected to carry the quarter-tonne, lead lined coffin, based on their height and fitness.
The tallest were put at the back and the shortest at the front and practiced with piece of plasterboard, as well as the coffin itself.
Captain Williams says: 'I remember vividly arriving at Kensington Palace to collect the coffin and put it on the gun carriage. It was a very intimate affair.'
Earl Spencermade a public pledge that her 'blood family' would protect her two sons
His colleague, Corporal Philip Bartlett, who was 24 at the time, adds: 'We had all the maids….crying. They were all coming out of the house. The next minute the undertaker said 'the coffin is coming' and it rolled in between us.
'We heard that huge scream, 'Diana we love you'. It cut through all of us. '
In all, more than a million grieving people lined the route along with 20,000 police, the largest ever security operation in Britain. Their presence was as much about protecting Diana's coffin as it was about security of the crowds, as Sir Malcom Ross explains: 'There were the extremists. She had the odd fanatic that would probably have tried to lie on the coffin or try something ridiculous like that.'
Such was the public hysteria, Captain Williams admits: 'I was genuinely seriously worried whether we would make it all the way.'
Pallbearer Corporal Philip Bartlett was one of the eight Welsh Guards chosen to carry the quarter-tonne, lead lined coffin, based on their height and fitness
As the princess's coffin passed Buckingham Palace the Queen, in an extraordinary and unprecedented concession to public feeling at the time, was waiting outside her official royal residence and bowed as it went past.
Sir Malcom reveals: 'I think the Queen thought that it was an opportunity to demonstrate to the world how involved she was.'
By the time they reached Westminster Abbey the guardsmen had been marching for two hours and then had to place the coffin on their shoulders, the first time they had felt its full weight.
Captain Williams says the men were in agony, having been rubbed red raw during rehearsals. 'The guys all had field dressings under their tunics because the rehearsing had rubbed away a lot of skin. So I knew they were in a fair amount of discomfort. You could see it on their faces. '
Captain Richard Williams who led the pallbearers, recalled the public hysteria and said he feared they wouldn't make it into the Abbey without being accosted
Corporal Bartlett recalls: 'I was trying to keep my mind off the pain and then we had the steps to go up to. We only dropped the coffin once in the rehearsals and we got it taken straight off us when we banged it, we caught it on one of the doors going into the gymnasium in Chelsea barracks.
'When we actually got into the cathedral [sic] and we stood for two minutes I could really feel the weight and the pain in my heels as well. I kept thinking to myself this is going to go if we don't start moving now. It felt like it was going to go. '
As the soldiers moved in, he revealed, the studs and metal plates on their boots began to slide on the marble and they lost their footing, causing the coffin to sway.
Out of view from the cameras, they managed to synchronise themselves again, however, and disaster was averted.
Although none of the cameras were allowed to focus on the Royal Family, Captain William noticed them as they walked past.
'What we saw was a family obviously sad and grieving, ' he says.
Diana: The Day Britain Cried, ITV, 29 August at 8pm