British detectives secretly listened in as Portuguese police grilled Kate McCann over daughter Maddie's disappearance, The People can today reveal.

They hid in a room next to the interview suite at the police station to watch the mother's every response to her gruelling interrogation.

It is understood the Brit officers even fed the local cops with questions through tiny earpieces - and used body-language experts to monitor Kate's reactions.

The People has discovered that Kate and husband Gerry were made official suspects after:

Local cops set up surveillance teams to monitor their movements 24 hours a day for three weeks.

Kate was hauled back in for a tough second interview after they claimed she had dramatically CHANGED her version of events.

The body-language experts compiled a secret report which is thought to suggest her demeanour indicates she has something to HIDE.

Emails and computer data are thought to have been closely examined.

The dramatic twists in the case of four-year-old Maddie come after Portuguese investigators received guidance from Britain's FBI, the Serious and Organised Crime Agency.

A dossier of covert electronic and physical evidence coupled with forensic reports led to the McCanns both being labelled suspects.

A source close to the inquiry revealed: "Following the request by the Portuguese to the British police to get involved the pace of the investigation has massively increased.

"Many of the failures made by local cops have been highlighted by the Brits and they are now working hard to find out what exactly happened to Madeleine."

The source explained: "It is common practice for those closest to a missing person to be watched closely and the McCanns are now no different.

"They, like all suspects, are being closely monitored as no stone is left unturned."

But GP Kate and cardiologist Gerry, both 39, fear they are being FRAMED over the disappearance and possible death of Madeleine - missing for 129 days. Police launched their round-the-clock surveillance operation last month.

The couple were taken in for further questioning last week after it was claimed that forensic experts had found traces of Madeleine's blood in the boot of a Renault Scenic car hired 25 days AFTER she went missing.

Detectives suspected Kate might have accidentally killed her daughter in the family's holiday flat in Praia da Luz and hid the body - which was later moved in the car.

Kate was grilled by Portuguese police for 11 HOURSon Thursday and for FIVE MORE HOURS on Friday.

It is understood she was forced to return for the second day of questioning at the police station in Portimao after cops claimed she changed her story - making them suspect she was being untruthful.

The British cops are also thought to have arranged for Kate's demeanour to be constantly monitored for any tell-tale signs during the long sessions of questioning. The People can also reveal that body language experts from Bramshill Police College in Basingstoke, Hants, put together a report on the McCanns' behaviour after studying hours of TV footage.

The specialists scrutinised every interview - live and recorded - given by the couple since May 3.

Asecret dossier of the findings has been handed to detectives leading the investigation.

It is believed the report concludes that Kate's body language and facial expressions in interviews show she has something to hide. Our source said: "Technology and policing methods have advanced so much in the last fewyears that officers can nowcall on all sorts of techniques in their investigations.

"Reading suspects' body language and their facial expressions is one such device. Both Kate and Gerry would have been looked at and their actions analysed."

But the source stressed: "It must be made clear that their movements could indicate they have not done anything untoward rather than helping to prove they have." Since Madeleine disappeared the anguish of her parents - who also have two-year-old twins - has been laid bare for the world to see.

At the first press conference, after the tot had been missing for only a few hours, the couple were visibly shook up and stressed.

Gerry did all the talking. Kate stood with her head bowed, clutching her husband's arm and saying nothing.

Since then, the confidence of the parents has grown. They put their careers on hold as they organised a massive and slick publicity campaign and even met the Pope. The McCanns rarely faltered as they gave interviews to media from around the world.

But as the Maddie investigation enters a dramatic new phase, the couple have now dropped plans to return home to Rothley, Leics.

Pals say they will stay in Portugal to clear their names.

A spokesman for the Portuguese police refused to comment last night on British involvement in the case.

But a source said: "We will continue to work with the British until we reach a satisfactory outcome."

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