A woman engaged to one of the failed July 21 London suicide bombers was jailed for three years on Friday for helping him escape the capital dressed in her mother's burqa.

Fardosa Abdullahi, 20, had given Yassin Hassan Omar the head-to-toe covering to help him flee to Birmingham the day after he tried with three others to detonate rucksack bombs on underground trains and a bus in 2005.

The plot was a copy of the suicide attacks in London two weeks earlier that killed 52 people but their home-made explosives failed to detonate properly.

Each was subsequently jailed for a minimum of 40 years.

Abdullahi, who was 18 at the time, had only become engaged to Omar four days before the attack.

CCTV cameras had captured her 6 foot 2 inch (1.88 metre) fiancé at a north London coach station covered in the burqa and carrying a handbag.

To aide his disguise he had also shaved his arms, but was arrested in Birmingham five days later.

Sentencing Abdullahi at the Old Bailey, Judge Paul Worsley rejected her plea not be jailed on the grounds that she was now pregnant, was vulnerable at the time of the offence and had a long history of mental illness.

"The message must go out that this court will not go soft on those who assist terrorists even those who are young, vulnerable and under pressure, as you undoubtedly were," Worsley said.

Abdullahi had pleaded guilty on June 5 to a charge of assisting an offender.

Her sentencing closes a series of cases in which 16 people have either been convicted of or admitted charges linked to the July 21, 2005 attacks.