A mystery donor has ensured that the key suspect in Madeleine McCann's disappearance will walk free from prison, it has been revealed.

Christian Brueckner is the main suspect in the unsolved disappearance of three-year-old Madeleine McCann, who vanished from her family's holiday apartment in Praia da Luz, Portugal, in May 2007.

The 48-year-old, who is currently serving a seven-year jail sentence in Germany for the 2005 rape of an American woman, then 72, in the same Algarve resort, is set to be released on September 17.

Investigators, who suspect that Brueckner played a part in young Madeleine's disappearance, had initially hoped to keep the German national behind bars due to an outstanding €1,446 fine from a previous conviction in 2015.

If Brueckner were unable to pay it, he would have been forced to serve another 56 days of 'alternative imprisonment', with it hoped that the extension of his jail sentence would help buy investigators more time to bring fresh charges in the McCann case.