Abu Qatada could be back on streets during Olympics in latest legal bid

But they will also ask for a writ of habeas corpus freeing him from custody.

The common law procedure developed in medieval times and is Latin for “you may have the body”.

It effectively calls for a detained person to be brought before the court for judges to decide if they are being unlawfully detained.

It was designed to provide protection against unfair detention, especially in feudal times, but is rarely used in modern times.

If the court grants a writ, it would mean a hearing to decide whether he should be released would have to be heard within a short time period.

Qatada, who is said to have wide and high-level support among Islamic extremists, was convicted in his absence in Jordan of involvement with terror attacks in 1998 and faces a retrial in his home country.

Theresa May, the Home Secretary, restarted deportation proceedings in April after she received assurances from the Jordanian authorities that evidence obtained by torture would not be used against him.

Qatada is now challenging those assurances at Siac and his legal team say they will take the battle back to the European courts if Siac rules against him at a tribunal hearing fixed for October.

Qatada, who is accused of involvement in several bomb attacks, is being held at high-security Long Lartin Prison in Worcestershire.

Edward Fitzgerald QC, representing Qatada, argued at the Siac hearing in May that it would be "quite wrong" if he had to remain in prison pending his deportation challenge.

But Mr Justice Mitting said: "I'm satisfied that managing the risk posed by the appellant outside a category A prison during (the Olympics) would be exceptionally problematic."

Repeated failed attempts by UK governments over the last 10 years to deport the radical cleric have cost nearly £1 million in legal fees, Government figures show.