Skins actor Daniel Kaluuya is suing the Met for assault and false imprisonment after he was wrongly suspected of being a drug dealer.
Police believe Madeleine could still be alive, and they have drawn up a list of 38 people - 12 of them British - who they want to speak to.
What happened to Madeleine? It is likely only one person knows the answer, and finding that person is the focus of a British investigation.
The Independent Police Complaints Commission (IPCC) said it has asked the family of a Hillsborough victim if they would like it to investigate recent allegations made against the UK's most senior officer, Sir Bernard Hogan-Howe.
The IPCC wrote on Twitter:
Portuguese investigation will run in parallel with Met's Operation Grange #McCann
AC Rowley: "This is a welcome development but both investigations at relatively early stages, with much work remaining to be done" #McCann
The Prime Minister has welcomed an investigation by British detectives into the disappearance of Madeleine McCann.
I think it is welcome but it is obviously a matter for the police. It is welcome because they say that there is new evidence, new leads to follow, new things to be done. It was a case that did shock and still shocks the nation and if an answer can be found we should try and find it.
A Scotland Yard detective has revealed that they are investigating 38 people in connection with the disappearance of Madeleine McCann.
Robin Dent, Rothley Parish Council clerk said: "Any news on it must be good news, we just hope that this time something will come of it, obviously everybody thinks of the family around here, we just hope something good comes out."
The McCann family has welcomed the Metropolitan Police's shift from a review to an investigation into missing Madeleine.
– McCann family statement
It is clearly a big step forward in establishing what happened and, hopefully, towards bringing whoever is responsible for Madeleine's abduction to justice.
In an interview with Channel 5 News, former Madeleine McCann suspect Robert Murat has spoken about the difficulty he faced in moving on from the accusations.
The Algarve-based businessman was named as a suspect in the disappearance of Madeleine from Rothley in Leicestershire in 2007, and was cleared in July 2008.
In the interview he said: "I've tried to move on, my family's tried to move on but it's always something I'm linked to.
"Whenever there's anything that's new my name gets mentioned it it so yes, I'd like to see it resolved."
Metropolitan Police Detective Chief Inspector Andy Redwood has said told ITV News that moving from a review to an investigation in the Madeleine McCann case was "an important moment" for the missing girl.
He said drawing together the material obtained by Scotland Yard, Portuguese authorities and private investigators had increased their investigative leads from 195 to over 3,800.
Metropolitan Police Detective Chief Inspector Andy Redwood has said there was "no clear definitive proof Madeleine McCann is dead" and urged the public to continue looking for the missing girl.