A retired RUC officer hired by Kate and Gerry McCann to find their missing daughter believes someone living in or around Praia da Luz — the Algarve resort where Madeleine McCann vanished — knows what happened to her.

Dave Edgar is one of the two retired British detectives hired by Kate and Gerry McCann to track down their daughter Madeleine.

The retired Cheshire and RUC detective, and Arthur Cowley, who spent 30 years with forces in the north west of England, have shifted the focus of their search back to the Portuguese resort where she went missing two years ago after details emerged of a second possible sighting of her and the abductor.

The detectives are reviewing 30,000 files released by the Portuguese authorities after the investigation was shelved last year and have signalled they will concentrate on Praia da Luz, believing that the answer lies within nine miles of the town.

The renewed effort came as the McCann family marked the second anniversary on Saturday of Madeleine’s disappearance during a holiday on the Algarve on May 3, 2007. The couple and their four-year-old twins, Sean and Amelie, spent the day privately while prayers were said at Sacred Heart church in Rothley, which they attend regularly.

The detectives have uncovered a statement from a family who said they saw a man carrying a small blonde child near the McCanns’ apartment on the night Madeleine vanished.

It corroborates the account of Jane Tanner, one of the couple’s friends, who said she saw what she is now convinced was Madeleine being carried away by her abductor.

She gave a description to the Portuguese police at the time, but they were initially reluctant to make it public because of judicial secrecy laws and only did so after the threat of legal action.

Mr Edgar said: “There’s someone local who has the answer to this, and not much wider than 10 to 15km (six to nine miles) from Praia da Luz. This offence happened in Praia de Luz. It’s a very self-contained resort. That’s where we’ve started and that’s where I think the answer is.”

“So you don’t start an investigation in Morocco or Spain or France or even Lisbon. This offence happened in Praia de Luz. It’s a very self-contained resort, and that’s where we’ve started and that’s where I think the answer is.

A reconstruction of the events of May 3 will be screened in a Channel 4 Cutting Edge documentary on Thursday.

The investigators hope the documentary and a reconstruction filmed with Gerry McCann may jog the memories of people who were in Praia da Luz at the time of the apparent abduction.

Mr Edgar said: “We’re interested in getting back and getting answers to where it happened and that’s why we’re doing a reconstruction, because there’s lots of unanswered questions.”

Key events in a tumultuous two-year investigation

Here is a timeline of the key events since Madeleine McCann’s disappearance.

May 3 — Kate and Gerry McCann, from Rothley, Leicestershire, leave their three children asleep in their holiday apartment in Praia da Luz while they dine with friends at a nearby tapas restaurant. Nothing is amiss when Mr McCann checks on the youngsters at just after 9pm, but when his wife goes back at about 10pm she finds three-year-old Madeleine missing.

May 5 — Portuguese police reveal they believe Madeleine was abducted but is still alive and in Portugal, and say they have a sketch of a suspect.

May 14 — Detectives take Anglo-Portuguese man Robert Murat in for questioning and make him an “arguido”, or official suspect.

August 6 — A Portuguese newspaper reports that British sniffer dogs have found traces of blood on a wall in the McCanns’ holiday apartment.

August 11 — Exactly 100 days after Madeleine disappeared investigating officers publicly acknowledge for the first time that she could be dead.

September 7 — During further questioning of Mr and Mrs McCann, detectives make them both “arguidos” in their daughter’s disappearance.

2008:

February 4 — Portugal’s top detective, Alipio Ribeiro, says in a radio interview that police were “hasty” in making Madeleine’s parents suspects in her disappearance.

July 21 — The Portuguese authorities shelve their investigation and lift the “arguido” status of the McCanns and Mr Murat.

2009:

April 22 — The McCanns fly to the US to record an interview with chat show host Oprah Winfrey to mark two years since Madeleine’s disappearance.