The 96-year-old’s death certificate had stated she died of ‘old age’ (Picture: PA)

The Queen had battled painful cancer in the final year of her life, a friend of Prince Philip has claimed in a new book.

Gyles Brandreth, writing in Elizabeth: An Intimate Portrait, shed light on the late monarch’s ‘stoicism’.

He claimed she had suffered from a form of bone marrow cancer over the course of her final years.

The Queen’s death certificate had stated that she died of ‘old age’.

It also confirmed that only the Princess Royal would have been by Her Majesty’s side in her final moments.

The death certificate, released by National Records of Scotland, noted the time of the Queen’s death on Thursday September 8 as 3.10pm.

Quotes from Elizabeth: An Intimate Portrait have been obtained by MailOnline, suggesting what had caused the monarch’s health to deteriorate.

According to the outlet, Mr Brandreth wrote: ‘I had heard that the Queen had a form of myeloma — bone marrow cancer — which would explain her tiredness and weight loss and those ‘mobility issues’ we were often told about during the last year or so of her life.

The late monarch suffered from mobility issues over her last year (Picture: PA)

‘The most common symptom of myeloma is bone pain, especially in the pelvis and lower back, and multiple myeloma is a disease that often affects the elderly.

‘Currently, there is no known cure, but treatment — including medicines to help regulate the immune system and drugs that help prevent the weakening of the bones — can reduce the severity of its symptoms and extend the patient’s survival by months or two to three years.’

The royal biography, serialised in the Daily Mail, also delved into how the Queen was forced to ‘go on’ following the death of her beloved husband.

It was said that the late monarch had found ‘a new comfort’ with Prince Philip in one another’s company during lockdown.

Queen Elizabeth spent her final days at her much-loved Balmoral estate in Scotland (Picture: Reuters)

Once restrictions lifted, they travelled to Scotland and Sandringham, as well as at Windsor.

The biography also detailed the Queen’s ‘determination’ to be with Prince Philip when he died.

It claimed she ‘barely left his side’ in the final few weeks of his life.

A period of ‘intense personal grief’ soon followed, but the Queen was said to have found huge comfort in her loved ones and believed it was her ‘Christian duty’ to carry on.

‘Life goes on. It has too,’ she said.

Her Majesty’s love for Line of Duty helped distract her, with such TV dramas working to ‘keep her spirits up’ after the Duke of Edinburgh’s death.

But, it’s thought that she sometimes struggled to keep up with the plot, which saw stars including Vicky McClure, Martin Compston, and Adrian Dunbar attempt to fight corruption,

The Queen also disliked the constant ‘mumbling’ on it and other programmes.

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A friend of the late Prince Philip made the comments in a new biography.