Who is Christian B?
Christian B is currently serving a seven-year prison sentence in Germany for the 2005 rape of an elderly woman in the same resort Madeleine disappeared from two years later.
He was arrested in Italy in 2018 and is due to be released from prison in September.
He has not been formally indicted or charged with any offence related to the McCann case and denies any involvement.
But in 2022, Portuguese police named him an 'arguido' in their investigation into Madeleine's disappearance, which makes him a formal suspect and gives him the right to silence and appropriate legal representation.
He moved to Portugal in 1995 after serving a two-year prison sentence in Germany for sexually assaulting a six-year-old girl in 1994. He lived in a cottage in Praia da Luz.
Soon after the world's media descended on the resort in 2007, he moved back to Germany.
Police have previously claimed he made a 30-minute call from the same area just an hour before Madeleine disappeared.
He is alleged to have confessed on two occasions to kidnapping and sexually abusing the toddler - once to a friend in a German bar in 2017 and again to his prison cellmate in 2020.
There was no suggestion in either alleged confession that he killed her, and he continues to deny any involvement.