It has been almost 15 years since three-year-old Madeleine McCann disappeared from a holiday home in Praia da Luz, Portugal, leaving little to no trace.
The police investigation to find her, Operation Grange, has cost £12.5million and so far not produced any convictions in relation to the case.
But on Thursday, Portuguese police formally identified German national Christian B as a murder suspect.
Investigators believe the convicted sex offender killed Madeleine after abducting her where she had been staying with her parents, Kate and Gerry McCann, and younger siblings, Amelie and Sean.
Sources have claimed the decision was linked to the statute of limitations in Portugal which means those found guilty of crimes punishable by a maximum prison sentence of more than 10 years cannot generally be prosecuted there if 15 years have passed since the crime.
Watch: Portugal names convicted child abuse Christian B as formal suspect in Madeleine McCann case
Here are the main events since the toddler disappeared.
– May 3: Kate and Gerry McCann, from Rothley, Leicestershire, leave their children asleep in their holiday apartment in Praia da Luz in southern Portugal while they dine with friends at a nearby tapas restaurant.
Nothing is amiss when Mr McCann checks on the youngsters just after 9pm, but when his wife goes back at about 10pm she finds Madeleine missing.
Jane Tanner, one of the friends dining with the McCanns, reports having seen a man carrying a child earlier that night.
– 14 May: Detectives take Anglo-Portuguese property developer Robert Murat in for questioning and make him an “arguido”, or formal suspect – but this is later withdrawn.
– 11 August: Exactly 100 days after Madeleine disappeared, investigating officers publicly acknowledge for the first time that she could be dead.
– 7 September: During questioning of Mr and Mrs McCann, detectives make them both “arguidos” in their daughter’s disappearance – but this is also later withdrawn.
– 9 September: The McCanns fly back to England with their two-year-old twins Sean and Amelie.
– 21 July: The Portuguese authorities shelve their investigation and lift the “arguido” status of the McCanns and Robert Murat.
– 12 May: Mrs McCann publishes a book about her daughter’s disappearance, on Madeleine’s eighth birthday.
Scotland Yard launches a review of the case after a request from Home Secretary Theresa May, supported by Prime Minister David Cameron.
– 25 April: Scotland Yard detectives say they believe Madeleine could still be alive, release an age-progression picture of how she might look as a nine-year-old, and call on the Portuguese authorities to reopen the case, but Portuguese police say they have found no new material.
– 4 July: Scotland Yard confirms it has launched its own investigation, Operation Grange, into Madeleine’s disappearance two years into a review of the case. It has “genuinely new” lines of inquiry and has identified 38 people of interest, including 12 Britons.
– 24 October: Portuguese police confirm that a review of their original investigation has uncovered new lines of inquiry, and they reopen the case.
– 29 January: British detectives fly to Portugal amid claims they are planning to make arrests.
– 3 June: Sniffer dogs and specialist teams are used to search an area of scrubland close to where Madeleine went missing.
– 12 December: Detectives begin questioning 11 people who it is thought may have information on the case.
– 16 September: The Government discloses that the investigation into the disappearance of Madeleine has cost more than £10 million.
– 28 October: Scotland Yard cuts the number of officers working on the inquiry from 29 to four.
– 30 April: The McCanns prepare to mark 10 years since their daughter’s disappearance with a BBC interview in which they vow to do “whatever it takes for as long as it takes” to find her.
– 3 May: Local media reports say Portuguese detectives are investigating a foreign paedophile as a suspect in the abduction of Madeleine.
– 3 June: Police reveal that a 43-year-old German prisoner, later named as Christian B, has been identified as a suspect in Madeleine’s disappearance.
– 4 June: Scotland Yard’s Operation Grange, which had received £12.3 million in funding up to April 2020, is still a missing person inquiry as detectives have no “definitive evidence whether Madeleine is alive or dead”.
– 4 May: Kate and Gerry McCann post a statement on the Official Find Madeleine Campaign website saying they still cling to the hope of seeing their daughter again as they prepare to mark her 18th birthday on May 12.
– 21 April: Christian B now 44, is made an “arguido”, a formal suspect, by Portuguese authorities.