Watch: Prince Philip: William and Harry united in their respect for their Grandpa
It will be a royal funeral like no other.
With only 30 mourners, their faces covered with masks and socially distanced from one another, Prince Philip's ceremony will look markedly different to any other royal occasion.
Coronavirus regulations have dramatically altered the way the funeral will be held, with the suggestion the Queen may even have to sit alone as she says her goodbyes to her husband of 73 years.
She has been living in Windsor Castle for most of the last year in what has been dubbed "HMS bubble", with a reduced number of staff and aides who support her.
None of her family members are in the castle bubble, and even her son Prince Charles had to make do with an Easter walk outside when he visited her briefly a few days before his father's death.
But lawyers have said it would be "reasonable" for the Queen to have someone to sit by – with one suggestion it could be Prince Harry.
Harry, 36, is understood to have arrived on his own from the US to attend the funeral on 17 April.
Under current regulations, he will be in quarantine, and will have taken at least two, if not three, coronavirus tests by the time he is released on compassionate grounds to attend the service.
If he were considered a single-person household, he could form a bubble with the Queen.
Adam Wagner, a human rights barrister, told Yahoo UK: "It is all guidance, none of this is law – that's the starting point.
"It has to be proportionate, she is 94, presumably quite frail, as much as she does not let on. There is not strict law requiring her to socially distance.
"Harry is presumably alone – if he is, she could sit with him."
Wagner added: "It is much too legalistic a reading of the guidance to think that she would not sit next to anybody, this is only guidance.
"She is vulnerable by any reading of the regulations.
"The law does not apply to her – it is all about appearances. There is no prospect the police would apply these.
"If she was 40 it would be different, but she is 94 – what if she faints? It is not about mastering the rules, it is about common sense."
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In a tweet, he added: "The fact that The Queen is a vulnerable person within the meaning of the regulations (she is well over 70) and this is likely to be a hugely difficult event for her would, I would suggest, mean that it was reasonable to sit someone next to her."
He also said that because there are about six different ways to form linked households, or bubbles, there is almost certainly a formation of family groups that could allow her to sit by someone at the funeral.
That doesn't include the fact that someone from HMS bubble is likely to be there. Brigadier Archie Miller-Bakewell, who worked for the Duke of Edinburgh for 11 years, is thought to be attending.
He could sit with her as he is already part of her household.
Some of the ways people can form bubbles under the regulations include for childcare, which is there for those with children under the age of one.
That currently applies to two couples within the Royal Family. Princess Eugenie's baby August was born in February, and Zara Tindall's baby Lucas was born in March.
Difficulties might arise if the new mothers have already formed bubbles.
And Harry, while likely to be on his own from the US, is in quarantine in Frogmore Cottage, where Eugenie and Brooksbank are understood to be living since they welcomed their son.
Solicitor Karen McAtamney of KJM Legal tweeted: "I'd have argued she does live alone, the same way a disabled adult with visiting carers/PAs is still a single adult household.
"I can see no definition of 'household' in the Regs. Staff who are with her for 'work purposes' arguably don't become part of her household.
"The more important point is the actual risk of COVID transmission indoors with 29 other people (plus some people working there) to an elderly woman, for whom vaccination might have been less effective than for younger people."
The Queen will have had both her COVID vaccinations now, as she confirmed that she had her first one more than 12 weeks ago.
The government guidance is that adults receive the second dose within 12 weeks of the first.
She carried out an in-person engagement two weeks ago on 31 March, and is likely to have been fully vaccinated by that point.
As a 94-year-old, the Queen certainly meets the government's definition of a vulnerable adult, which includes anyone aged over 70.
The funeral guidelines published on the government website advise mourners to keep their distance from anyone who is "clinically extremely vulnerable".
Harry can attend the funeral despite having to be in self-isolation, under exemptions provided in the guidelines.
The government website explains: "If you are legally required to self-isolate, you may only break self-isolation to attend a funeral if it is of a close family member (for example, a partner, parent, sibling, child or grandparent)."
Harry, having come from the US, will have had to show a negative coronavirus test before he boarded the plane. He will then have to take two during quarantine in the UK.
And if he decides to take part in the private test and release scheme, he could take one on day five of his quarantine and be able to leave early if it is negative.