Queen Elizabeth II's death certificate has confirmed her formal cause of death was "old age", and revealed exactly when she passed away, shedding new light on the timeline of that tragic day.

The certificate, part of which was released by the National Records of Scotland on Thursday night, Australian time, confirms that Her Majesty died at 3.10pm on September 8 (2.10am, Friday September 9 NZT) at Balmoral Castle. Old age is the only cause listed.

The document shows the official informant was the Queen's daughter Princess Anne, who was at her bedside when she died.

Elizabeth II's death was registered in Aberdeenshire on September 16.

An extract of the Queen's death certificate. Photo / National Records of Scotland

The revelation that she died at 3.10pm adds more context to the efforts senior royal family members, including her grandsons William and Harry, made to reach her bedside.

Her son Prince Charles - now King Charles III - arrived at Balmoral at 10.30am (9.30pm Thursday NZT), joining his sister, Princess Anne. They would ultimately be the only family members to make it in time.

A public statement from Buckingham Palace, which revealed doctors were concerned for the Queen's health and set off a storm of media coverage, was issued just after 12.30pm.

Her Majesty was still alive when the RAF plane carrying Prince William, Prince Andrew, Prince Edward and his wife Sophie, Countess of Wessex, took off for Balmoral at 2.39pm. That flight had been scheduled to leave at 1.30pm, but suffered a mysterious delay.

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Queen Elizabeth II last official portrait released on September 18 on the eve of her funeral. Part of her death certificate has been released. Photo / Royal Family

The group landed in Aberdeen at 3.50pm. By the time they arrived at Balmoral Castle, after 5pm, the Queen had been dead for about two hours.

Prime Minister Liz Truss was told at 4.30pm.

Then there is William's brother, Prince Harry, who didn't take off from Luton Airport in Bedfordshire until 5.35pm. Some British publications later reported Harry was told of his grandmother's death only minutes before the 6.30pm announcement to the public.

This would mean he only found out more than three hours after it happened.

Prince William and Kate, Princess of Wales, left, and Britain's Prince Harry and Meghan, Duchess of Sussex view the floral tributes for the late Queen Elizabeth II outside Windsor Castle. Photo / AP

Harry's plane finally landed at 6.46pm, and he reached Balmoral at 7.52pm.

The revelation that Elizabeth II died at 3.10pm raises fresh questions about when, exactly, Charles told Harry not to bring his wife Meghan, the Duchess of Sussex, to Scotland.

"Charles told Harry that it wasn't right or appropriate for Meghan to be in Balmoral at such a deeply sad time," a source told The Sun in the days after the death.

"It was pointed out to him that Kate was not going and that the numbers really should be limited to the very closest family. Charles made it very, very clear that Meghan would not be welcome."

Harry and Meghan issued an initial announcement that they would be flying to Scotland together at 2pm. He ended up leaving London more than three hours after that.

People queue outside as Windsor Castle and St George's Chapel on September 29. The castle has reopened to public for first time since Queen Elizabeth II's death. Photo / AP

The news that Meghan would not be joining him emerged via Omid Scobie, a journalist close to the Sussexes, at 4.44pm.

"A source has shared an update stating that only Prince Harry has made the trip up to Balmoral," Scobie wrote on social media.

We now know that was more than 90 minutes after the Queen's death.

She was buried with her late husband, Prince Philip, in St George's Chapel after being farewelled at a sombre state funeral earlier this month.

People are still queuing at Windsor Castle to visit Her Majesty's resting place.