Royal historian Andrew Lownie believes the decision to remove the former Duke of his titles did not come from the monarch or the Duke himself – but rather King Charles‘ heir, Prince William.

After another week of scandal, Andrew was finally forced to relinquish all of his remaining royal titles tonight, stepping down from membership of the Order of the Garter and giving up his Duke of York title.

He also lost his position as Knights Grand Cross of the Royal Victoria Order but will remain a prince, while his ex-wife, Sarah, the former Duchess of York, also lost her titles and will now be known simply as Sarah Ferguson.

But royal historian Andrew Lownie, who published an unauthorised biography of Prince Andrew in August called ‘Entitled’, revealed tonight that he believes the decision came from an unexpected source – the throne’s heir, Prince William.

Speaking to the BBC, Lownie said: ‘Andrew certainly hasn’t driven it [the decision to give up his titles].

‘I mean, if he was thinking of his family, as he claims, he would have done something like this many years ago. It’s not really coming from King Charles either.

‘It’s coming from William and the government I understand who felt that this was a distraction from the wider work of the royal family.’

He added: ‘I think there’s much more still to come out. And I think that was what was worrying them that that they were best to distance himself before, before these new allegations arose.’

The news of Andrew’s demotion tonight follows a frosty exchange witnessed between Andrew and Prince William at the Duchess of Kent’s funeral last month.

The disgraced Duke of York tried to engage in conversation with his nephew after the pair paid tribute to Katharine Kent in a service at Westminster Cathedral.

Andrew could be seen muttering a few words to William, who appears to decline to engage in the conversation and only gives a brief nod in response.

Body language expert Judi James told the Daily Mail that Prince William’s ‘non-verbal responses’ suggest a degree of ‘awkwardness’ between the pair.

She also described the expression on Prince Andrew’s face as he tries to chat to his nephew as a ‘smug-looking smile’.

The prince’s decision tonight to give up his titles was made after strong pressure from King Charles and in discussion with other family members, including Prince William, as heir to the throne, as well as Andrew’s other siblings, Princess Anne and Prince Edward.

But there was also an air of weariness that the monarchy had been forced to endure another week of deeply damaging headlines at the disgraced duke’s hand.

Lownie said the demotion ‘doesn’t change very much.’

‘It protects his daughters. They retain their titles. I think something has to be seen to be done. And this seemed a very neat solution,’ the historian said.

‘But I think there’s still many questions. I mean, he still, I think, holds the rank of, Vice-Admiral Navy. He’s still living in Royal Lodge.’

Lownie added that he believes the title stripping is probably a compromise decision.

‘As long as he can stay in Royal Lodge, as long as can have the shooting weekends, I think he’ll be content with this. This is probably a compromise position.

‘I mean he basically, in return for spending 10 million pounds on doing up Royal Lodge, has been given a peppercorn rent there and a long lease, and it’s going to be quite difficult to get him out of about the optics look.

‘But I think, again, if he’s thinking of his family and the wider interests of the monarchy, he should be departing from Royal Lodge,’ Lownie said.

It is understood that the King, who is believed to have spoken to his brother by phone from Scotland about the issue, feels ‘glad’ at the outcome. ‘Something had to be done,’ a source said.

In a statement issued by Buckingham Palace on his behalf, Andrew made clear he continued to deny allegations of sexual assault made against him by the late Virginia Giuffre, who he met through paedophile financier Jeffrey Epstein.

But he conceded continued revelations about his dealings with Epstein, as reported by The Mail on Sunday, were a ‘distraction’ from the good work of the Royal Family.

Prince Andrew said his decision was prompted by his desire to ‘always… put my duty to my family and country first’ – echoing his infamous comment that he chose to break off relations with Epstein by flying to New York to tell him the news personally, because he was an ‘honourable’ man.

Tonight, in a statement, the family of Ms Giuffre, who took her own life in April, said Andrew’s decision was ‘vindication for our sister and survivors everywhere’.

They added: ‘This moment serves as victory for Virginia, who consistently maintained, ‘He knows what happened, I know what happened, and there’s only one of us telling the truth, and I know that’s me’.’

Prince Andrew’s ex-wife, Sarah, Duchess of York, with whom he will continue to live at the lavish 30-bedroom Royal Lodge at Windsor, will now be known as simply Sarah Ferguson.

Lownie claimed Sarah will be the real loser of the decision, losing all of her titles while her ex-husband will remain a Prince by birthright.

‘I think it will be a blow to Sarah Ferguson. I mean, she’s capitalized on being Duchess of York for the last 40 years, even long after they were divorced.

‘I mean, if she’s used actually some of her brand products, so are Duchess products. So I think for her money-making activities, it’s going to be a bit of a blur.

‘In a statement issued by Buckingham Palace on his behalf, Andrew made clear he continued to deny allegations of sexual assault made against him by the late Virginia Giuffre, who he met through paedophile financier Jeffrey Epstein.’

Last weekend, the MoS exclusively revealed that Prince Andrew had publicly lied when he claimed he never had contact with Epstein again following a ‘final’ meeting with him in December 2010.

It obtained emails sent 12 weeks after that meeting in which Andrew contacted the sex offender to reassure him, the day after a picture of the prince with Ms Giuffre was published, that ‘we are in this together’ and would have to ‘rise above it’.

Sickeningly, Andrew concluded: ‘Otherwise keep in close touch and we’ll play some more soon!!!’ It was signed ‘A, HRH The Duke of York, KG’, as a knight of the Order of the Garter.

It was also revealed that Andrew met, on at least three occasions, the alleged Chinese spymaster at the centre of the current Whitehall espionage case.

Sources have told the Daily Mail that things came to a head this week after a ‘constant drip, drip’ of fresh claims, of which the MoS’s email revelations proved the ‘most significant issue’. The changes will take effect immediately and were decided upon in recognition of the fact that the prince’s personal issues continued to be an ‘unwelcome distraction’ from the work of the wider Royal Family.

However, the King has acknowledged that he cannot legally force Andrew out of his Royal Lodge home and he will continue to remain there so long as he can afford the rent.

The prince has a 100-year-plus private tenancy agreement with the Crown Estate which is said to be ‘unaffected’ by issues relating to his honours and titles.