Although criticised by London as crude and unacceptable manipulation, the release of letters and video has certainly dominated media coverage of the standoff over the last few days.

"They have got everyone's attention. They are clearly getting things out, using the girl because they know in the West that's a soft spot," said Paul Beaver, a leading defence expert.

"I don't like it but I think they're doing very well."

The "girl" in question is 26-year-old Faye Turney, the sole woman among the eight sailors and seven marines seized at gunpoint on March 23 in the northern Gulf.

She has become the human face of the standoff, in particular since she was shown in television footage Wednesday -- complete with dark Islamic veil -- admitting that the 15 had "obviously" strayed into Iranian waters.

Three letters have since been released purporting to have been written by her, reflecting for many the successive hardening of the Iranian position.

In the first, released Wednesday, she asked her family not to worry because she was "strong." In the second she questioned why British forces remain in Iraq.

In the third, released Friday addressed in odd-sounding English "To British People" (sic), she lamented that she and her colleagues had been "sacrificed" to US and British policy -- and compared their good treatment in Iran to the inmates of Iraq's notorious Abu Ghraib prison.

Britain insists Turney is being coerced.

"I really don't know why the Iranian regime keep doing this. All it does is enhance people's sense of disgust," said Prime Minister Tony Blair on Friday. "Captured personnel being paraded and manipulated in this way doesn't fool anyone."

Turney's body language in Wednesday's video certainly suggests she is under pressure: she answers the interviewer blankly and smokes intensely, in stark contrast to the "chatty" and "outgoing" woman described by those who know her.