Scotland Yard joins hunt for Madeleine

London: Scotland Yard joined the hunt for Madeleine McCann last night after her parents begged David Cameron for help.

Kate and Gerry McCann made an anguished personal plea to the Prime Minister to intervene, warning: "We are at the end of our tether."

Within hours of their desperate appeal, Home Secretary Theresa May announced that Scotland Yard would help Portuguese police review key evidence about Madeleine's disappearance, aged three, from an Algarve resort in 2007.

The McCanns believe potentially vital clues were missed in the botched Portuguese investigation, which was formally shelved in 2008. The Portuguese have been reluctant to reopen the failed inquiry into Madeleine's disappearance but they have now agreed that the Met should lead a review of the evidence.

It is not clear whether British officers will travel to Portugal.

The McCanns have previously asked three Home Secretaries for help, including May. If new leads or missed opportunities are thrown up, the inquiry could be formally reopened, Government sources said.

Ministers hope the Metropolitan Police (Met) team can bring a ‘new perspective' to the controversial case and have agreed that the Home Office will fund their work, which will be conducted in tandem with Portuguese police.

But the move has prompted questions about why the review could not have been carried out earlier, when evidence was fresher. And critics will question whether there is any realistic prospect of a breakthrough in the case, which has seen no major developments since Madeleine's disappearance on May 3, 2007.

May said: ‘The Government's primary concern has always been and remains the safe return of Madeleine. Although she disappeared in Portugal, and the Portuguese retain the lead responsibility in the case, law enforcement agencies here have continued to follow up leads and pass information to the Portuguese authorities as appropriate.

"The Prime Minister and I have today agreed with [Met boss] Sir Paul Stephenson that the Metropolitan Police will bring its particular expertise to this case. Clearly, the detail of what that will entail will be a matter of operational judgment."