On the morning of his 66th birthday, Andrew Mountbatten-Windsor received some unexpected visitors.

It was the police.

The former prince has been arrested on suspicion of misconduct in public office and an investigation has been opened.

He has since been released from police custody, with the disgraced royal photographed leaving a police station via car after 7pm.

This is the first time Andrew, who has previously denied any wrongdoing in his associations with the late convicted sex offender Jeffrey Epstein, has been arrested.

He is the first senior British royal in modern history to be arrested. The last time a British royal was arrested was almost 400 years ago when King Charles I was detained in 1647 during the English civil war, before his execution in 1649.

Andrew has continued to vehemently deny any wrongdoing. No charges have been made at the time of writing.

The investigation is ongoing. This is what we know so far.

Unmarked police arrested Andrew at Sandringham estate.

Local reporters captured the moment vehicles — believed to be unmarked police cars — arrived at Sandringham Estate in Norfolk.

He has been living there since leaving Royal Lodge earlier this month.

The BBC reports he was arrested around 8am on Thursday morning in England.

Listen: Andrew Mountbatten-Windsor Arrested On Suspicion Of Misconduct In Public Office. Post continues below.

Police statement.

The Thames Valley Police released a statement on Andrew's arrest without directly naming the former Prince.

The statement, cited by the BBC, read: "As part of the investigation, we have today (19/2) arrested a man in his sixties from Norfolk on suspicion of misconduct in public office and are carrying out searches at addresses in Berkshire and Norfolk."

An investigation has been opened.

Upon his arrest, an investigation was opened.

"Following a thorough assessment, we have now opened an investigation into this allegation of misconduct in public office," Assistant Chief Constable Oliver Wright said, per the BBC.

"It is important that we protect the integrity and objectivity of our investigation as we work with our partners to investigate this alleged offence."

According to local reports, police were spotted undergoing searches at Andrew's former residence, the Royal Lodge.

King Charles III: "The law must take its course."

In the wake of Andrew's arrest, his brother King Charles III released a statement expressing that "the law must take its course."

"I have learned with the deepest concern the news about Andrew Mountbatten-Windsor and suspicion of misconduct in public office," he said.

"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."

Charles added that police "have our full and wholehearted support and co-operation."

"Let me state clearly: the law must take its course," he continued.

"As this process continues, it would not be right for me to comment further on this matter. Meanwhile, my family and I will continue in our duty and service to you all."

The arrest was the result of reports made.

The police earlier said it was "assessing" reports that the former prince sent confidential government trade reports to convicted sex offender Jeffrey Epstein in 2010.

The assessment followed the release of millions of pages of documents connected to a US investigation of Epstein.

Mountbatten-Windsor features a number of times in the documents.

Watch: The Quicky unpack the new photos of Andrew in the Epstein Files. Post continues below.

Following reports of this assessment, the king made a statement throwing his support behind the police.

"The King has made clear, in words and through unprecedented actions, his profound concern at allegations which continue to come to light in respect of Mr Mountbatten-Windsor's conduct," a Palace spokesman said, per the BBC.

"While the specific claims in question are for Mr Mountbatten-Windsor to address, if we are approached by Thames Valley Police we stand ready to support them as you would expect."

The Palace spokesperson told the BBC the King and Queen's "thoughts and sympathies have been, and remain with, the victims of any and all forms of abuse."

King and Queen continue with royal duties.

Despite the news of Andrew's arrest, the King and Queen got on with their royal duties both attending separate engagements.

According to the BBC, they both avoided answering questions about Andrew's arrest.

Andrew was released from police custody.

Hours after his initial arrest, Andrew was pictured leaving a police station.

Photographers captured the former prince leaning back in the back seat of a car as they drove away from Aylsham police investigation centre just before 7pm British time, per the BBC.

On his release, Thames Valley Police released another statement confirming that "the arrested man has now been released under investigation", per the BBC.

They also confirmed that "searches in Norfolk have now concluded."

Andrew's fall from grace.

The former prince first stepped back from his royal duties in 2019 following his infamous sit-down interview with BBC's Newsnight about his friendship with the late convicted sex offender Epstein.

Last October, Andrew announced he would no longer use his title of Duke of York and honours following a discussion with King Charles. The King then proceeded to officially rescind his brother's titles, including his title as Prince, and announced that he would be required to move out of Royal Lodge — the home he lived in with his ex-wife Sarah Ferguson.

"Prince Andrew will now be known as Andrew Mountbatten-Windsor," a statement from the Palace said stressing that "their Majesties wish to make clear that their thoughts and utmost sympathies have been, and will remain with, the victims and survivors of any and all forms of abuse."

It came as calls continued to grow for the former prince to face an investigation over his friendship with Epstein.

While it was announced in late October, Andrew only just moved out of Royal Lodge earlier this month. He now resides in the Sandringham Estate in Norfolk — a property privately owned by the King. The BBC reports the King will pay the costs of Andrew's new home.

The Guardian previously reported the former Duke of York was set to receive a large one-off payment and an annual stipend as part of his new life as a commoner.

— with AAP.

Feature image: Getty.