Prince Harry didn't answer calls the night his grandfather, Prince Philip, died

Prince Harry learned of his grandfather's death after a knock on the door in the early hours of the morning from a Santa Barbara Sheriff. Photo / File

Prince Harry learned of the sad news his grandfather had died when he was visited by police after sleeping through calls in the early hours of the morning.

Police knocked on the door of his California home after he didn't pick up calls from the US Embassy officials around 3am to tell him of Prince Philip's death, TMZ claims.

An embassy representative reportedly called the sheriff's department in Santa Barbara and requested an officer be sent to the home of Prince Harry and his wife Meghan Markle in Montecito, The Sun reports.

Harry was finally told of Prince Philip's death after a police officer arrived at the gates and told him to call the Embassy urgently.

Prince Harry learned of his grandfather's death after a knock on the door in the early hours of the morning from a Santa Barbara Sheriff. Photo / File

It's not known whether his phone was on silent, turned off, or if he and Meghan slept through the calls.

Prince Philip died on the morning of April 9 at Windsor Castle and the news was announced by Buckingham Palace in a statement at 12pm UK time. In LA, it would have been 4am.

It's understood the Royal Family was desperate to tell Harry of the death personally to spare him the distress of learning the news in the media first, The Sun reports.

The Duke of Sussex released a poignant tribute to his grandfather last month, calling him a "master of the barbecue, legend of banter, and cheeky right till the end".

Harry flew home to the UK to attend the funeral without wife Meghan, who is pregnant with their second child and was advised not to travel by her doctors.

Prince Harry flew home to the UK to attend the funeral for Prince Philip. Photo / AP

Philip died just a month after Meghan and Harry's bombshell interview with Oprah Winfrey aired.

During the controversial interview, the pair made allegations that a senior royal had made a racist comment about the colour of their son Archie's skin while Meghan was still pregnant.

Oprah later clarified neither the Queen nor the Duke of Edinburgh had been responsible for the comment.

Prince Harry, Duke of Sussex, appears in a scene from new documentary series 'The Me You Can't See'. Photo / Supplied

Meghan also told the chat show host she had no longer wanted to be alive while pregnant with her firstborn.

The revelations made during the interview are thought to have made the royal family even more eager to alert Harry of Philip's death.