The unit said the main suspect declined to interview in a high-profile case of Madeleine McCann’s disappearance.

The Metropolitan said the international request letter had been sent to Christian Brückner, who was about to release another offence, which he later refused.

Brückner, 48, has never been charged with any crime related to the McCann case and has denied any involvement.

Madeleine disappeared in 2007 in the Portuguese resort of Praia da Luz. She and her siblings have been sleeping in a holiday apartment while parents Kate and Gerry eat at a nearby restaurant.

They checked the child regularly until Kate discovered that Madeline was missing around 22:00.

Brückner is currently serving seven years in Germany for the rape of a 72-year-old woman at her home in Praia da Luz in 2005.

German authorities say he Will be released on Wednesday.

Det Ch Insp Mark Cranwell said Brückner remains a suspect in Metropolitan Police’s investigation into Madeleine’s disappearance. He has been the main suspect in investigations in Germany and Portugal since 2020 and 2022.

“We have requested an interview with the German suspect, but for legal reasons, it can only be done through an international request letter submitted,” Det Ch Insp Cranwell said.

“The suspect then refused. Without an interview, we will continue to conduct any viable inquiry lines.

“We cannot provide more information when conducting the investigation.”

Madeline’s disappearance has become one of the unresolved cases of missing persons in the world.

German prosecutors pointed out that evidence, including cell phone data, suggests that Bruckner may have been in the area when the area disappeared and has been insisting that they think they are responsible.

However, they have not found enough evidence to file the charges.

Brückner spent many years in the Algarve, a homeless man, a small criminal and convicted sex offender. He has had several previous convictions, including sexual abuse of children in 1994 and 2016.

Portuguese and German police conducted a brand new search between where the McCanns stayed and addresses related to Bruckner, but this was from June this year No breakthrough.