What charge might King Charles' brother face after his arrest?

King Charles' younger brother Andrew Mountbatten-Windsor was arrested on suspicion of misconduct in public office this week, over allegations that he sent confidential British government documents to disgraced financier Jeffrey Epstein.

Thames Valley Police, whose detectives questioned the former prince all day on 20 February, have said they are looking into allegations that Mountbatten-Windsor had passed documents to the late convicted US sex offender while working as a trade envoy.

Among files relating to Epstein released by the US, some suggest that Mountbatten-Windsor forwarded to Epstein in 2010 reports about potential business opportunities in places he had visited as the Special Representative for Trade and Investment.

The former prince, who turned 66 on 20 February, has always denied any wrongdoing in relation to Epstein. He was released from custody late on 20 February while the investigation continues.

Here are details about the potential charge he faces:

What is misconduct in public office?

The offence of misconduct in public office is a 'common law' offence, meaning it is not covered by written legislation but has been developed over centuries by judges' rulings.

A conviction for misconduct in public office carries a maximum sentence of life imprisonment. Police have previously said the offence involves "particular complexities" that require a careful assessment, without elaborating further.

Britain's top prosecutor Stephen Parkinson said this month that the law on misconduct in public office is "quite clear".

However, the offence has largely been used against lower-ranking police and prison staff, according to research published last year by campaign group Spotlight on Corruption, which said prosecutors might struggle with complex offences.

In one case, a former policeman was handed a 10-month jail sentence in 2013 for selling a story to The Sun newspaper and trying to sell another, about the child of celebrities, to the now-defunct News of the World.

The independent Law Commission in 2020 recommended replacing the offence of misconduct in public office and a law is currently going through parliament to do so, though it would not have retrospective effect.

What do prosecutors have to prove?

Tom Frost, a law lecturer at Loughborough University, said misconduct in public office "remains a difficult offence to prove in relation to senior executives or senior political figures".

Firstly, prosecutors have to show that an individual was in a public office and "acting as, not simply whilst, a public official" at the time of an alleged offence.

As Mountbatten-Windsor's trade envoy role was unpaid - though he received free travel and accommodation - the case for arguing he was acting as a public official might be less clear, though guidance from the Crown Prosecution Service says remuneration is "not determinative".

Prosecutors also need to prove that a defendant wilfully misconducted themselves "to such a degree as to amount to an abuse of the public's trust".

The Court of Appeal said in 2003 that the bar is a high one and that the conduct had to be "not merely negligent but ... an affront to the standing of the public office held".

Misconduct in public office also requires that the conduct had no reasonable excuse or justification.

What happens next?

Given the complexity of misconduct in public office, it is likely that police and prosecutors will take several weeks or even months to make a decision on whether to bring charges.

Mountbatten-Windsor, who has always denied any wrongdoing in relation to Epstein but has not spoken publicly since the release of further files, might well face further questioning.

In the event that he is charged, the former prince would have to attend a magistrates' court for his first appearance.

Misconduct in public office can only be tried by a judge and jury, meaning Andrew's case would be sent to the Crown Court, which handles the most serious criminal cases, most likely the famous Old Bailey in central London.

There are long-standing delays in the British criminal courts, with some trials currently being listed as far ahead as 2030, though any trial of the king's brother would most likely be heard sooner.