As Portuguese police fly to the UK to listen in on interviews with the so-called "Tapas 7", what is known about the people who are key witnesses in the disappearance of Madeleine McCann?

The seven friends who dined with Kate and Gerry McCann on the night of Madeleine's disappearance are the central witnesses in this case.

Their evidence has been pored over by the police, and their backgrounds closely scrutinised by journalists and bloggers alike.

None of the seven is a formal suspect or "arguido". and all have cooperated willingly and voluntarily with the investigation. Bound by judicial secrecy laws, most have made no public comment about what they saw.

Their friendship goes back a long way. Four of the group - Matthew Oldfield, Russell O'Brien, David Payne and Fiona Payne - studied medicine together at Leicester University in the early 1990s - the Paynes becoming a couple.

Timeline

Doctors Kate and Gerry McCann moved to Leicestershire in 2000, and quickly became part of the medical social circle.

Three other holidaymakers completed the table at the poolside tapas restaurant on 3 May last year: Rachael Oldfield (married to Matthew), Jane Tanner (partner of Russell O'Brien) and Diane Webster (Fiona Payne's mother).

The couples had travelled to the Algarve from East Midlands and Gatwick airports, together with eight young children.

Following Madeleine's disappearance, the nine adults collectively provided the police with a timeline of the evening.

As far as they were concerned, the timeline was a common sense means of speeding up the investigation; but elements within the Portugal's Policia Judiciaria (investigating police) seem to have interpreted the move as a closing of ranks.

Either way, the timeline is absolutely key to understanding what might have happened to Madeleine.

This is how the group recalled the evening:

·    1730: Kate and Gerry McCann pick up their three children from afternoon tea at the Ocean Club ·    1800: Gerry begins a game of tennis with other guests ·    1840: David Payne checks on Kate and the children, at Gerry's request and sees Madeleine ·    1900: Gerry finishes playing tennis   ·    2035: Kate and Gerry McCann arrive at the Ocean Club's tapas restaurant   ·    2105: Gerry checks on his children, and sees Madeleine alive and well   ·    2115: Having left the table to check on her own children, Jane Tanner sees a man carrying a child, close to the McCanns' apartment   ·    2130: Matthew Oldfield checks on the McCanns' apartment. Hearing no noise from the children's bedroom, he assumes all is well and leaves without seeing Madeleine   ·    2200: Kate McCann checks on her children. Madeleine is gone.

Key witness

Arguably the most significant witness is Jane Tanner.

She has already given detectives a detailed description of a man she saw, close to the ground floor corner apartment where the McCanns were staying.

She says he was carrying a child, dressed in pinkish pyjamas - the same colour that Madeleine was wearing that evening.

The man has never come forward or been traced by the police, leading the McCanns to conclude that Jane Tanner almost certainly witnessed their daughter being abducted.

Last November, Ms Tanner told the BBC's Panorama programme: "I know what I saw, and I think it's important that people know what I saw - because I believe Madeleine was abducted."

Based on her account, the McCanns produced an artist's impression of the man, in the hope that it might jog the memory of other holidaymakers.

Of the remaining friends, David Payne was the last person - besides Kate and Gerry McCann - to see Madeleine alive that evening, so his recollection of timing is crucial.

Matthew Oldfield was the only group member, beyond Madeleine's parents, to enter the McCanns' apartment during the dinner.

If Jane Tanner did unwittingly see Madeleine's kidnapper, the timeline suggests that the abduction took place before Mr Oldfield made his check.

But not having set foot in the children's bedroom, he cannot be sure of whether the little girl was there or not.

Finally, three of the group have offered significant evidence relating to Robert Murat, the third arguido in the case.

Russell O'Brien, Fiona Payne and Rachael Oldfield all say they saw Mr Murat later that evening, during the frantic search for Madeleine.

Their testimony is directly at odds with his assertion that he was at home with his mother all night. Robert Murat says the McCanns' three friends are, at best, confused; and, at worst, lying. But they, in turn, remain certain of what they saw.