King Charles should admit what he knew about Andrew Mountbatten-Windsor’s misconduct, when he found out and what he did about it, a royal expert has said. 

The monarch’s younger brother was arrested on the morning of his 66th birthday on Thursday over suspicions of misconduct in public office. 

It came amid the ongoing fallout over Andrew’s friendship with paedophile billionaire Jeffrey Epstein – with Charles said to have become increasingly concerned about allegations against his brother. 

But after the Mail on Sunday revealed the King was warned as long ago as 2019 that the Royal Family’s name was being ‘abused’ by Andrew’s business associations, royal expert Andrew Lownie has insisted Charles must admit how much he knew. 

Mr Lownie, author of Entitled: The Rise and Fall of the House of York, said: ‘I suspect we may see other charges being laid on Andrew in the course of the next few months.

‘I think it will be very damaging if it is revealed that King Charles knew about this. And, you know, I think he needs to come clean on what he knew, when he knew it and what he did about it. 

‘Because if he’s been covering this up, then I think his position will become very difficult.’ 

Following his brother’s arrest on Thursday, Charles issued an unprecedented statement confirming his ‘wholehearted support and co-operation’ with the investigation into Andrew. 

The King added: ‘I have learned with the deepest concern the news about Andrew Mountbatten-Windsor and suspicion of misconduct in public office.

‘What now follows is the full, fair and proper process by which this issue is investigated in the appropriate manner and by the appropriate authorities. In this, as I have said before, they have our full and wholehearted support and co-operation.

‘Let me state clearly: the law must take its course.’

But following a raid on Andrew’s new and former homes on Thursday, the future of the royal family has been thrown into doubt as revelations about how much Charles may have known rise to the surface. 

Mr Lownie added: ‘There’s a sort of culture of fear in the States about doing anything. 

‘But, you know, we’re very lucky that this was initiated by the police. And, you know, they said they would do it without fear and favour. 

‘No one’s above the law. And I’m afraid that that feeling doesn’t exist yet in the States. But I think as more names emerge and it’s seen that people are being held to account in this country, we may see some of the people in the States being brought to justice.’ 

Buckingham Palace declined to comment.  

Today, the Mail on Sunday revealed Charles was warned in as early as 2019 that the Royal Family’s name was being exploited by Andrew’s business associations. 

In a bombshell email, a whistleblower told the Palace that the former Duke had secret financial links to controversial millionaire financier David Rowland, who was abusing his royal links. 

Messages seen by this newspaper also appear to show that Andrew allowed Mr Rowland to effectively join in with his official duties. 

The cache of emails threaten to draw Charles further into the crisis, triggered by Andrew’s links to Epstein, and allegations he passed potentially confidential and sensitive documents to the convicted paedophile.  

On Thursday, Thames Valley Police confirmed Andrew had been arrested that morning, with officers able to hold him without charge for 24 hours from the time he arrived at a police station. 

He was later photographed in the back of a car leaving Aylsham police station in Norfolk shortly after 7pm. 

The Daily Mail was the first to reveal that plain-clothes police, carried in six unmarked vehicles, had arrived at Wood Farm, where Andrew now lives, at around 8am on Thursday.