First Sea Lord, Admiral Sir Jonathon Band, also accused Iran of exerting "psychological pressure" on the eight sailors and seven marines who returned to emotional reunions in Britain on Thursday after 13 days in detention.

Band said an official inquiry would look at the rules of engagement, intelligence gathering, equipment and procedures to prevent any repeat of the March 23 capture.

Until a comprehensive review is complete, the Royal Navy has suspended all boarding operations in the area of the kind that the Britons were carrying out when seized, he added.

Band rejected suggestions that the 15 should not have made "confessions" to their captors for allegedly breaching Iranian territorial waters, and only have given their name, rank and serial number.

The inquiry is to look into the alleged confessions made by some of the group, including the only woman, Leading Seaman Faye Turney.

"They weren't on combat operations. They weren't like people shot down in Tornados in the (first) Gulf War," the head of the Royal Navy said.

"I don't think there is any doubt from the statements some of them made, and certainly the letters, that they were under a certain element of psychological pressure.

"I think you will find out that they were actually a brave set of youngsters."

On Thursday, Royal Marines officer Lieutenant Colonel Andy Price said some of the group may have been left in solitary confinement during their detention, despite their appearance together on Iranian television.

The sailors spent their first night of freedom at the Royal Marine Base Chivenor in Devon, southwest England, after being reunited with their families.

They are being debriefed and undergoing medical examinations. Some of the group are due to address a news conference at 1400 GMT. In a joint statement released Thursday, the group said their ordeal had been "very difficult".

A military inquiry was under way to determine how they came to be captured as they conducted what Britain said were routine anti-smuggling operations near the Shatt al-Arab waterway dividing Iraq and Iran.

One of the 15, Royal Marine Captain Chris Air, told Sky News television in an interview recorded a week before their detention that British crews did gather intelligence on Iranian activities in the Gulf area.

In his BBC interview, Band dismissed suggestions that the 15 had surrendered too easily and that they should have fought back against their captors.

"I think our people have reacted extremely well in some very difficult circumstances," he said, adding that the decision to board and search a merchant ship that led to their seizure was "absolutely proper".

"I think they acted with considerable dignity and a lot of courage," he added.