The Duke of Cambridge and the Duke of Sussex will be reunited behind closed doors at Windsor Castle before laying their beloved grandfather to rest.
Members of the royal family including Prince William and Prince Harry will gather in the State Entrance Hall before the Duke of Edinburgh's coffin emerges from the State Entrance at 2.41pm on Saturday (1.41am Sunday NZT).
Assuming the brothers have not arranged a private meeting earlier on Saturday morning, it is the first time they will see each other in the flesh in over a year.
It will also mark their first face-to-face meeting since Harry and his wife Meghan gave an interview to the US chat show host Oprah Winfrey last month, suggesting an unnamed royal had queried Archie's skin tone as well as describing William as "trapped" in the monarchy.
In an apparent sign of ongoing tensions between the brothers, they will not walk shoulder to shoulder in the funeral procession but will be separated by their cousin Peter Phillips, the Queen's eldest grandchild.
After walking behind Prince Philip's coffin to the west steps of St George's Chapel, they will then be split up again when they make their way to the pews in the Quire for the 3pm ceremony.
They are not expected to sit together during the 50-minute, Covid-compliant service, which will require royals who do not live together to be spaced two metres apart and all members of the 30-strong congregation to wear face masks.
As The Telegraph revealed on Tuesday, William, 38, is understood to have spoken with Harry, 36, on the telephone since he landed in the UK from Los Angeles on Sunday.
They have not been able to see each other any earlier because Harry has had to spend the week in quarantine at Frogmore Cottage, his former Windsor home, while the Cambridges have been spending the Easter holidays at Amner Hall, their home on the Queen's Sandringham estate in Norfolk.
Sources close to both brothers insist they will be putting their differences aside for the sake of the Queen as the family gathers to remember the Duke, who died on Friday at the age of 99. One well-placed insider said: "The entire focus is on the Queen. No exceptions. A family unified."
As well as having Phillips, 43, act as mediator, it is thought the Duchess of Cambridge – who Prince Harry once described as "the big sister I never had" – will also try to play the role of peacemaker.
On Thursday, the 94-year-old Queen stepped in to soothe tensions by ordering that none of the royals wear military dress.
It came amid concerns that Prince Harry, who relinquished his military ties after standing down as a senior royal in March 2020, could have faced the embarrassing prospect of being the only senior royal not in uniform despite twice serving on the frontline in Afghanistan.
It also followed ructions caused by the Duke of York demanding to go dressed as an Admiral, despite his promotion to that rank being deferred after he stepped back from public duties in November 2019 over his relationship with the convicted paedophile Jeffrey Epstein.
Members of the royal family, Prince Philip's family and his close friend Lady Mountbatten of Burma, who are not taking part in the procession, will depart Windsor Castle by car for the short drive to the 15th century chapel at around 2.20pm UK time (1.20am Sunday NZT), with those left in the procession mingling behind closed doors.
Precisely 21 minutes later, Prince Philip's coffin will emerge from the State Entrance, with royals walking in the procession then taking up their positions. The Prince of Wales will walk with his sister, the Princess Royal, with their siblings the Duke of York and the Earl of Wessex following behind.
Princes William and Harry will then flank Phillips, with Princess Anne's husband, Vice-Admiral Sir Timothy Laurence, bringing up the rear alongside the Queen's nephew, the Earl of Snowdon, the son of the late Princess Margaret.
Once the coffin – which is being convened on a customised Land Rover hearse specially designed by the Duke – arrives at the chapel at 2.53 pm (1.53am Sunday NZT), there will be a national minute's silence before it is carried through the Nave to the catafalque in the Quire.
After putting on face masks, royals who walked in the procession will then pair up to take their pews. Prince William will walk with Phillips while Prince Harry will walk with the Earl of Snowdon.