Her Majesty would have found the service an ordeal which represented a turning point for the monarchy, Professor Sarah Richardson added.
The Monarch, 94, sat alone today as she laid the Duke of Edinburgh, who stood by her side for seven decades of unwavering service, to rest.
University of Warwick's Prof Richardson said: "To some extent this is the end of a period. The Queen will carry on and she will carry on doing her duty, she's already gone back to work to some extent.
"I think she will step back more and more, she's in her mid-90s. Seeing her there solely on her own, when she's been accompanied by Philip for 70-odd years, I think it represents a turning point."
Our stoic Queen went back to work four days after Prince Philip died aged 99 last Friday.
She marked the retirement of her household's most senior official.
* Prince William requested that Peter Phillips stand between him and his brother on the way to Prince Philip’s funeral, it has been claimed.
* Kate Middleton today acted as a peacemaker between Prince Harry and William.
* Prince Charles has plans to take Prince Harry for a walk around Windsor to look at tributes for the Duke of Edinburgh.
* Meghan Markle left a handwritten note to Prince Philip
* The Duchess of Sussex watched the funeral from the US after not being able to fly to the UK for the service
* The Duke of Edinburgh's coffin was lowered into the Royal Vault
Prof Richardson added: "She has a really strong sense of service and duty and protocol and she's attended many funerals in the past and she strongly follows the rituals and so on.
"In some ways it would have been comforting for her that the Duke of Edinburgh played such a strong role in planning and organising the service but it must have been an ordeal at the very least."
Just 30 mourners attended Philip's funeral at St. George's Chapel, Windsor this afternoon due to Covid rules.
While the Queen sat alone for the service, members of the Royal Family were also present, including her four children Prince Charles, Princess Anne, Prince Edward and Prince Andrew.
And Princes William, 38, and Harry, 36, came face-to-face for the first time since the Duke of Sussex quit royal life - and since his explosive Oprah Winfrey chat.
The pair were kept 12ft apart as they walked behind Prince Philip's coffin, separated by Princess Anne's son Peter Phillips, 43 - a pal of both.
And they were sat opposite each other in the chapel.
But the brothers, who both walked behind their mother Princess Diana's coffin in 1997, shared a private moment and chatted after the service.
Professor of modern British history Sarah Richardson insisted that William and Harry's chat would have been intentional.
She said: "The whole family apart from the Queen walked back to the castle from the chapel.
"The fact that Harry walked with William and Kate I think was perhaps a symbol that there is at least a willingness to talk and perhaps have some rapprochement between the two princes."
Kate Middleton, 39, paid tribute to Princess Diana by wearing Her Majesty's pearl choker which was previously lent to her late mother-in-law.
While The Queen often wore the priceless necklace during the 1980s, she leant the four-strand choker to Princess Diana for a state banquet in the Netherlands in 1982.