The British monarchy woke up to a new reality on Friday, after one of their own, Andrew Mountbatten-Windsor, a younger brother of King Charles III, was arrested on suspicion of misconduct in public office.

Mountbatten-Windsor, one of the late Queen Elizabeth II and Prince Philip's four children, spent some 11 hours in police custody Thursday as he was held and questioned at a police station not far from his new home on the king's privately owned Sandringham Estate in Norfolk, England.

Mountbatten-Windsor -- known as Prince Andrew before being stripped of his royal titles and honors last October -- was released Thursday without charge. He remains under investigation though after the emergence of documents released by the U.S. Justice Department, which show communications between Mountbatten-Windsor and the late convicted sex offender Jeffrey Epstein.

Watch Impact x Nightline, "The Prince, The Predator and The Arrest," now streaming on Disney+ and Hulu.

Thames Valley Police, the department that arrested Mountbatten-Windsor, say they are continuing to search Royal Lodge, Mountbatten-Windsor's former home on the grounds of Windsor Castle, for evidence, including computers and other electronic devices. The former prince left Royal Lodge and moved to Norfolk on Feb. 4, under orders from his older brother Charles.

Mountbatten-Windsor has previously denied wrongdoing with respect to Epstein. He has not spoken publicly since his arrest.

While he remains under investigation, whether or not Mountbatten-Windsor will be charged with a crime is a question that could take weeks to years to answer, according to Vicky Lankester, a solicitor specializing in criminal and regulatory defense with U.K. law firm Brett Wilson.

"This could be over very quickly, or it could be over in months, years. No one really knows," Lankester, who is not involved in Mountbatten-Windsor's case, told ABC News on Friday. "Andrew's been what's called 'released under investigation,' so that means there's no kind of, like, deadlines or anything that the police have to abide by."

Misconduct in public office is a charge that is rare in the U.K., according to Lankester.

"It's an offense contrary to common law, as opposed to any legislation making it a criminal offense, and guidance on the prosecution says that if you can, you charge someone with a statutory offense, as opposed to a common law offense, because it's easier and it's kind of fairer to all parties," she said. "So you don't kind of see these sorts of cases that often."

While Mountbatten-Windsor remains under investigation, he is not under any conditions, meaning he is free to travel and does not have to report to a court or police department, Lankester noted.

If Mountbatten-Windsor is charged with misconduct in public office, he will face a jury trial with a maximum penalty of life imprisonment.

Mountbatten-Windsor's arrest appears to relate to emails he sent Epstein during his time as the U.K. trade envoy in 2010. The emails, released by the U.S. Justice Department in January, suggest Mountbatten-Windsor may have allegedly discussed potential business dealings with the disgraced financier while working for the government.

Potential for future investigations

Looking ahead, Mountbatten-Windsor could face additional investigations, including a second one by Thames Valley Police.

"We are aware of reports about a woman said to have been taken to an address in Windsor in 2010 for sexual purposes," the department said in a Feb. 12 statement. "We are assessing the information and following established procedures to seek further information with law enforcement partners in the United States."

Thames Valley Police have not provided an update on that assessment.

Separately, London's Metropolitan Police announced on Feb. 18 that they are launching enquiries into allegations that members of Mountbatten-Windsor's royal protection team may have ignored illegal activity on Epstein's Caribbean island.

"Protection officers are held to the same high standards of professional behaviour as all police officers. At this time, we have not identified any wrongdoing by any protection officers. However, initial enquiries into these specific allegations have begun so we can establish the facts," the Met Police said in statement. "As with any investigation, should any new allegations come to light these will be assessed in the usual way. This includes any misconduct or criminal matters. It would be inappropriate for us to comment further while other enquiries related to these matters are ongoing."

Epstein died by suicide in 2019 while awaiting trial for allegedly sexually abusing dozens of girls in New York and Florida. He earlier served a 13-month jail sentence and work release, the result of a 2008 plea bargain with federal prosecutors in Florida.

Potentially losing his place in the line of succession

Another question hanging over Mountbatten-Windsor is his place in the royal family's line of succession.

Currently, he is eighth in line to the British throne behind Charles' two sons -- Princes William and Harry -- and their combined five children.

U.K. politicians are now debating whether they should introduce legislation to have Mountbatten-Windsor officially removed from the line of succession.

The Government will consider introducing legislation to remove Andrew Mountbatten-Windsor from the line of succession once the police investigation has concluded, ABC News understands.

"Changing the order of succession, having someone removed is extremely complicated," said ABC News royal contributor Alastair Bruce, adding that the easier route is for Mountbatten-Windsor to abdicate his spot.

"What the king might do is ask his brother to abdicate from it, which he can, but getting him forcibly removed, the king can't do that," he said. "Parliament can do it, but Parliament, quite frankly, is trying to get growth going in the United Kingdom. It's trying to deal with all the other ambitions of the present government. They really don't want to be spending time on the order of succession."

The arrest of Andrew Mountbatten-Windsor, the brother of King Charles III and son of the late Queen Elizabeth II, is threatening Britain's monarchy in an unprecedented way, royal experts say.

Mountbatten-Windsor, formerly known as Prince Andrew, was arrested Thursday, his 66th birthday, on suspicion of misconduct in public office, according to the Thames Valley Police

Mountbatten-Windsor was arrested at Sandringham estate, the king's estate, in eastern England. He was released under investigation on Thursday evening, according to Thames Valley Police, and has not been charged.

Watch Impact x Nightline, "The Prince, The Predator and The Arrest," now streaming on Disney+ and Hulu.

Buckingham Palace said Thursday that Charles was not informed ahead of his brother's arrest, which follows the emergence of documents detailing communication between Andrew and the late convicted sex offender Jeffrey Epstein.

Mountbatten-Windsor, the first senior royal arrested in recent history, has previously denied wrongdoing with respect to Epstein.

"It's undoubtedly a threat to the monarchy," ABC News royal contributor Robert Jobson said Thursday of Mountbatten-Windsor's arrest, noting the historic and "seismic" nature of a police raid taking place at a royal estate.

"I think some people, many people, younger people included, will argue, what is the point of an institution that's unelected when you've got criminality, or potential criminality, actually unfolding like this and members of the royal family being arrested and cautioned ... to give evidence under oath in an interview?" Jobson said on "Good Morning America." "It's shocking."

Charles, who ascended to the throne in 2022 following Elizabeth's death, called for the law to "take its course" in a statement issued Thursday by Buckingham Palace.

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

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

Charles' son Prince William, heir to the throne, and William's wife Kate, the Princess of Wales, did not issue a new statement following Mountbatten-Windsor's arrest, but ABC News understands they support the king's statement.

Just hours after news of Mountbatten-Windsor's arrest was made public, both Charles and his wife, Queen Camilla, attended public engagements -- Charles attending a fashion show and Camilla attending an orchestra performance -- though neither answered reporters' questions about Mountbatten-Windsor.

While the royal adage has long been to "keep calm and carry on," the royal family's commitment to continuing their duties has so far not moved the public discussion away from Mountbatten-Windsor, according to ABC News royal contributor Victoria Murphy.

"The focus on this over the past few years, and particularly the past few days, has been very damaging. What we've seen in the past few days is ... members of the royal family heckled on official engagements to an extent that we absolutely have not seen before," Murphy said Thursday, referring to recent incidents in which the queen and others have faced shouted comments about Mountbatten-Windsor.

"I think that really shows … that this is not just an issue, as they keep saying, for Andrew Mountbatten-Windsor, but it is also sparking huge discussion and debate around the monarchy as a whole," Murphy added.

Murphy described Mountbatten-Windsor's arrest as "potentially hugely damaging" for Britain's royal family, noting that anti-monarchy groups are using the fallout from Mountbatten-Windsor's ties to Epstein to renew their calls for an end to the monarchy.

"We're seeing very mixed opinions [in the U.K.] on how they're handling this and what they should do now," she said. "But we're all seeing a kind of resurgence in debates and discussions around monarchy itself, around this system that we have. People are really questioning that now."

Though Mountbatten-Windsor faced scrutiny for his ties to Epstein during Elizabeth's reign, it was not until his brother took the throne that Mountbatten-Windsor was arrested.

As king, Charles has already stripped Mountbatten-Windsor of his "style, titles and honours," including his prince title, and, more recently, evicted Mountbatten-Windsor from his longtime home, Royal Lodge, on the grounds of Windsor Castle.

Even with his titles stripped, Mountbatten-Windsor, as a child of the queen, remains in the line of succession, as do his daughters Princesses Beatrice and Eugenie and their combined four children. Mountbatten-Windsor is currently eighth in line to the throne behind William and his younger brother Prince Harry and their combined five children.

In addition to the fallout from Mountbatten-Windsor's arrest, Charles and his family may also face lingering questions from the public about what they knew and when, as it relates to Mountbatten-Windsor's ties to Epstein, according to Jobson.

Epstein-related documents released by the U.S. Department of Justice in January include correspondence between Mountbatten-Windsor and Epstein in 2010, after Epstein concluded a 13-month jail sentence and work release, the result of a 2008 plea bargain with federal prosecutors in Florida.

The documents also show the two men communicated beyond the time Mountbatten-Windsor said publicly that he had cut ties with Epstein.

"This cover-up, if it does turn out to be a cover-up, could be a real damage, serious damage to the royal family, because you've got to remember, this has been in the public domain for over 16 years," Jobson said, later adding, "This does not really look good for the institution, as well as the individual."