Kate and Gerry McCann say they know what contributed to daughter Madeleine's disappearance

It's been 16 years since three-year-old Madeleine McCann disappeared while holidaying with her family in Portugal.

The youngster was sleeping in her Praia da Luz, Lagos hotel apartment alongside her younger twin siblings, Sean and Amelie, that fateful night.

Since then, her parents Kate and Gerry McCann - who had been enjoying dinner at the Ocean Club restaurant when Madeleine disappeared - have refused to give up the search for their daughter.

And this week, after Portuguese police issued the McCann family an apology for the way they handled the initial investigation, a passage of Kate's 2011 book - Madeleine: Our Daughter’s Disappearance and the Continuing Search For Her - has been doing the rounds online.

In the memoir, mum Kate opened up on a 'bitter regret' that she and husband Gerry have harboured since the night of Madeleine's disappearance, after discovering a small but pivotal detail.

James Boardman Archive / Alamy Stock Photo.

The mother-of-three revealed that she had requested a specific table at the Ocean Club restaurant the night she disappeared that would allow the group a full view of the apartment in which their kids were sleeping.

Following Madeleine's disappearance however, Kate discovered that what had been written by the member of staff in the reservation book could have alluded to the fact that there were unsupervised children in the nearby apartment that night.

"To my horror, I saw that, no doubt in all innocence and simply to explain why she was bending the rules a bit, the receptionist had added the reason for our request: we wanted to eat close to our apartments as we were leaving our young children alone there and checking on them intermittently," she wrote.

PA

Kate added: "We now bitterly regret it and will do so until the end of our days."

Last week, it was reported that a group of senior officials travelled from the Portuguese capital of Lisbon to London to make a formal apology to the McCanns.

This was because back in 2007, just months after their daughter went missing, Kate and Gerry McCann were made 'arguidos' - or suspects - in the Portuguese investigation.

The husband and wife duo were questioned by detectives working on the case after it was initially assumed that they'd staged an abduction and concealed Madeleine's body.

Kate later claimed she'd been offered a deal to admit to covering up her daughter's death in exchange for a shorter sentence.

Despite the couple's arguido status being lifted in 2008, Kate and Gerry remained under suspicion in Portugal for years.