How Andrew's 11-hour detention on his birthday played out

We may never know if Andrew Mountbatten-Windsor was still in bed on the morning of his 66th birthday when the knock came at the door.

It was 08:00 GMT and several Thames Valley Police officers had driven three hours in unmarked cars to the Sandringham Estate to see him.

They had been sent to carry out perhaps the most extraordinary arrest in modern British history.

The force had the option of arranging for Andrew to present himself at a police station at a pre-arranged time to be arrested.

They chose not to use it.

The senior arresting officer would have then told him: "You do not have to say anything. But it may harm your defence if you do not mention when questioned something which you later rely on in court. Anything you do say may be given in evidence."

That recital began a day the likes of which no British royal has experienced in centuries.

It is unlikely Andrew would have been deemed a risk to the arresting officers or himself, or that he would try to escape, so he probably would have been spared handcuffs.

But it is possible he saw plain clothes officers filing into his home on the King's private Sandringham Estate to begin searching through his possessions.

It is even possible they brushed by him as he was being led away.

Uniformed officers stood guard around the property as the search continued throughout the day.

At the same time, police were descending on Royal Lodge, the mansion at Windsor Great Park that Andrew called home for 22 years, and which he was forced to leave earlier this month as public scrutiny over his ties with Jeffrey Epstein intensified.

There appears to have been more to look through for officers there.

Searching ended at Sandringham on Thursday but BBC News has learned they are expected to continue at Windsor until Monday.

Very few people knew about the imminent operation. Home Secretary Shabana Mahmood was informed ahead of time, BBC News understands, while the National Police Chiefs' Council was only informed minutes before.

Buckingham Palace was not told in advance.

However, the Times has reported that the Palace was informed after Andrew was detained but before the public statement confirming an arrest was released. Thames Valley Police has declined to dispute that report when contacted by the BBC.

Just before 10:00 GMT, BBC News revealed that Andrew had been arrested. Thames Valley Police confirmed an arrest shortly after.

By then, Andrew had been driven to Aylsham police station, a non-descript facility about 40 miles (64km) from where he was arrested.

It would have been up to the custody sergeant on duty to verify the suspect's identity - which, in the circumstances, will not have taken long.

Andrew may well have gone through the same booking in process as anyone else - a mugshot, fingerprints, a DNA swab - though there are limited circumstances in which these steps can be skipped, primarily if a suspect is extremely vulnerable, and there is some leeway on how these procedures are applied.

It is not clear what Andrew's guards would have been doing at this stage, or whether they would have accompanied him on the walk to his holding cell.

As the door on that cell swung open, Andrew would have seen a bare room containing little else but a bed and a toilet.

The Queen's third child would have been offered something to eat and a change of clothes if he wanted them.

Andrew would then have had a decision to make: take the legal advice of the 24/7 local duty solicitor, or draft in his own lawyer. We do not know which he chose.

Next, he would have been taken to an interview suite to be questioned under caution by senior detectives, though details of that encounter will only ever become public should Andrew be charged with an offence.

Eleven hours after he was first detained, Andrew was told he could leave. He was being released under investigation.

In practical terms, that means he was walking out a free man - no restrictions on his movement, no requirement to remain at an agreed address - but still very much as a suspected criminal.

A hitch at the police station meant Andrew's detention was slightly longer than it might have been.

The electric gates leading into the facility failed to open for Andrew's close protection officers, who arrived in three Range Rovers to collect him.

After ten minutes of staff trying to open the stuck gates, the vehicles were forced to reverse and find another way in.

It was Reuters photographer Phil Noble who captured the image which seems to tell the story of the day in a single frame.

Andrew is in the casual clothes he was wearing when police took him that morning. He is leaning back in an attempt to avoid the waiting cameras. His hands are held together over his chest.

And spread across his face, which is illuminated by the flash of the camera, is a look of shock, exhaustion - even horror.

Had the electric gates opened sooner, the photographer may not have made it in time to get the shot, and Andrew might have slipped away unseen.

At around 20:00, Andrew was back at the Sandringham Estate and heading for Wood Farm, where he is staying temporarily.

Renovation works continue on nearby Marsh Farm, which has been earmarked as his future home.

It is the place where the Royal Family intends for him to live out a quiet life in semi-official exile, away from the public gaze.

The events of Andrew's 66th birthday suggest that may not be possible.

Additional reporting by Matt Precey and Lucy Manning