Prince Philip was the person the Queen could "unburden herself" to when she was facing a "sea of problems", Sir John Major has said.
The former prime minister added the duke offered Her Majesty "great support" during their 73 years of marriage and his death will leave "an enormous hole" in her life.
He told BBC One’s The Andrew Marr Show: "Consider the position the Queen is in. She is the head of state, that is a very lonely position in many ways.
"There are a limited number of people to whom she can really open her heart, to whom she can really speak with total frankness, to whom she can say things that would be reported by other people and thought to be indelicate.
"Of the handful of people to whom she can speak frankly, her husband, Prince Philip, was obviously the first one.
"At times of difficulty, he was the person who was there, he was the person to whom she could unburden herself.
"And when you’re facing a sea of problems, as she so often was, and sometimes when you’re overwhelmed by what has to be done, someone who understands that, someone that can take part of the burden, someone who can share the decision-making, someone who can metaphorically – or in the case of Prince Philip, I think, probably literally – put their arms around you and say ‘it’s not as bad as you think, this is what we have to do, this is how we can do it, this is what I think’ – I think when you talk of him being a great support, that was it."
The Archbishop of Canterbury later said the Prince Philip showed a "remarkable willingness to take the hand he was dealt in life and straightforwardly to follow its call".
Justin Welby paid tribute to the Duke of Edinburgh at a remembrance service at Canterbury Cathedral following his death on Friday.
The archbishop said: "For the Royal Family, as for any other, no words can reach into the depths of sorrow that goes into bereavement.
"We all know that it is not simply a factor of age or familiarity. It is not obliterated by the reality of a very long life remarkably led, nor is the predictability of death’s arrival a softening of the blow. Loss is loss."
The archbishop continued: "For his Royal Highness the Duke of Edinburgh there was a willingness, a remarkable willingness, to take the hand he was dealt in life and straightforwardly to follow its call.
"To search its meaning, to go out and on as sent, to enquire and think, to trust and to pray."
Mr Welby later said during the service: "The duke would have been the first to harrumph strongly at over spiritualisation of the world he found, let alone of himself."
The archbishop also asked people to pray for Prince Philip, the Royal Family and others who are grieving.
He said: "Our lives are not completed before death… so we can indeed pray that the Duke of Edinburgh may rest in peace and rise in glory.
"We may pray for comfort. We may pray and offer love for all who find that a great life leaves a very great gap."
The archbishop had earlier praised Philip’s "righteous impatience" and "gift of moral imagination" at an online memorial at Lambeth Palace.
Dr John Sentamu, the former Archbishop of York, had earlier said it was a "pity" the Duke of Edinburgh will be remembered for his gaffes.
He told BBC One’s The Andrew Marr Show on Sunday: "I am sure he regretted some of those phrases, but in the end it is a pity that people saw him simply as somebody who makes gaffes.
"Behind those gaffes was an expectation of a comeback but nobody came back and the gaffe unfortunately stayed."
Dr Sentamu went on: "He would make an off-colour remark but if somebody challenged him you would enter into an amazing conversation.
"The trouble was that, because he was the Duke of Edinburgh, the husband of the Queen, people had this deference."
The UK is officially in a period of national mourning for the next week, up to and including Philip’s funeral on Saturday afternoon.
The Queen and her family will wear masks and practice social distancing as they gather to say their final farewell at St George’s Chapel, Windsor Castle.
Prince Charles spoke movingly of his "dear Papa" on Saturday and said the Royal Family are being helped through this "particularly sad time" by the public outpouring of support.
The Prince of Wales said his father, who was 99, had devoted himself to the Queen, his family and the country for some 70 years.