Watch: Queen left with ‘huge void in her life’ says Prince Andrew
For more than 73 years, he was her "strength and stay".
But at 94, the Queen is now a widow, after the death of her husband Prince Philip.
It's no secret she relied on the Duke of Edinburgh for advice and counsel over the years, and the death will leave a "huge void" in her life – as her son Prince Andrew said.
Who will step up to help fill that role as she continues as head of state and Commonwealth, and to whom can she turn in an hour of need?
Yahoo UK takes a look.
The Queen is said to have a good relationship with her only daughter Princess Anne, who was also close to Philip.
The two women, with their strong work ethics, will likely take comfort in one another, and the Queen will know in Anne she has someone strikingly similar to Philip.
Prince Andrew, the Queen's second son, is often reported to be her favourite child.
He spoke to reporters outside church in Windsor on Sunday and said of his mother: "She described it as having left a huge void in her life.
"But we – the family, the ones that are closer – are rallying round to make sure that we're there to support her, and I know there is a huge amount of support not just for her but for everybody as we go through this enormous change."
Andrew was also alongside the Queen in January 2020 in Sandringham after the deal between Harry and Meghan and other senior members of the Royal Family was struck, allowing them to step back.
He is clearly a key support for his mother in times of trouble.
The Queen's youngest son Prince Edward lives fairly close by in Bagshot Park, but it's his wife Sophie, the Countess of Wessex, who the monarch is particularly close to.
The two women reportedly talk at least once a day, and spend Saturday afternoons watching films together.
Lady Louise Windsor, Edward and Sophie's daughter, shared a love of carriage driving with her grandfather, and was reportedly seen on his carriage on 9 April, the day he died.
Sophie has previously said that her proximity to the Queen means the whole family can pop round for tea, something that may be of comfort to the Queen in the months to come.
Prince Charles, the oldest sibling and heir to the throne, has already been taking on more royal duties over the last few years as his mother scales back her work.
He will likely be taking on a new set of family responsibilities as well as supporting his mother in work duties.
Watch: Queen is ‘thinking of others before herself’
Her friends and aides
Outside of her family, the Queen keeps a close circle of friends. At nearly 95 herself, her circle is getting smaller.
One of those who she is close to is her dresser Angela Kelly.
Kelly, 62, has been by her side since 1993, and the Queen has even allowed her to write books about her role.
She has previously said she loves the Queen and that they have become "closer" over the years.
Another member of staff to whom the Queen is close is Paul Whybrew, nicknamed Tall Paul.
It was Whybrew who was on hand in the 1980s when the Queen found an intruder in her room – an event that was recently dramatised in season four of The Crown.
Whybrew has been in the Queen's HMS Bubble, the term given to the staff with her at Windsor Castle, in the last 12 months.
Lady Pamela Hicks, who is also one of Philip's cousins, is a close friend of the Queen. Lady Pamela was a bridesmaid for then-Princess Elizabeth when she married Philip and was a lady-in-waiting for her for several years.
Lady Pamela may be at the funeral on 17 April, and could be a key link for the Queen as she remembers her husband.
While Lady Pamela doesn't spend time with the Queen on engagements these days, she does still have ladies in waiting who provide help and friendship to her.
Among them are Lady Susan Hussey, who is also one of Prince William's godparents, Mary Morrison and Dame Annabel Whitehead, according to the Daily Mail.
In the coming days the Queen may seek some comfort in the great outdoors and her favourite pastime of riding.
Her head groom Terry Pendry will be on hand to accompany her around Windsor Great Park and provide a listening ear.