An Islamic extremist who recruited Britain's youngest terrorist over the internet has been jailed for 12 years.

Aabid Khan spent years building up a computer "encyclopaedia" of jihadist material including a file on various members of the Royal family when he met 15-year-old Muhammad Munshi online.

He encouraged the schoolboy to wipe out all non-Muslims.

The youngster, whose grandfather is a leading Islamic scholar, was 16 and in the middle of his GCSEs when arrested on his way home from school in 2006.

He had two bags of ball-bearings in his pockets and notes about martyrdom under his bed.

Munshi downloaded detailed instructions about making napalm, other high explosives, detonators, and grenades, and "how to kill".

The schoolboy then sent them to his mentor Khan and fellow cell member Sultan Muhammad, who also had a library of terror documents on his computer.

Home Secretary Jacqui Smith branded all three a "very real threat" following their convictions on Monday.

Khan, 23, a former fast food restaurant worker, of Otley Road, Undercliffe, Bradford, West Yorkshire, was found guilty of three count of possessing articles for a purpose connected with terrorism.

His cousin and "right-hand man", Post Office worker Muhammad, also 23, of Hanover Square, Manningham, was convicted of three possession charges and one of making a record of information likely to be useful in terrorism. He was jailed for ten years.

Munshi, now 18, of Greenwood Street, Saville Town, Dewsbury, was also found guilty of a making offence and will be sentenced next month.

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