Britain's youngest terrorist was behind bars yesterday after a guide to making napalm was found in the schoolboy's home.

Hammaad Munshi, just 16 when arrested, was drawn into the same shady world of internet fanatics as Scots student Mohammed Atif Siddique.

For nearly a year Munshi, whose grandfather is a leading Islamic scholar, led a double life. By day, he attended lessons at the local comprehensive and did as he was told. By night, he spent hours surfing jihadist sites and distributing online propaganda for what the Crown branded a "worldwide conspiracy" to "wipe out" non-Muslims.

Munshi was 15 when recruited by Aabid Khan, 23, a "key player" in radicalising the impressionable and vulnerable in the UK and abroad with his message of "violent jihad", including Siddique, the Scottish "wannabe" suicide bomber jailed last year.

Khan and another co-accused are expected to be sentenced today for terrorism-related offences. Munshi, now 18, was remanded after being free on bail throughout his trial. He will have to wait until next month to learn his fate but is expected to be jailed. Siddique was sentenced to eight years at the High Court in Edinburgh last year but is currently awaiting an appeal.

London's Blackfriars Crown Court heard the hard drive of a computer in Munshi's bedroom contained detailed instructions about making napalm, other high explosives, detonators, and grenades, and "how to kill". The schoolboy, who was born in Dewsbury, West Yorkshire, was arrested as he and friends returned from Westborough High School.

Khan, from Bradford, had been detained a day earlier, on June 6, 2006, at Manchester airport as he arrived home from a trip to Pakistan. He was carrying a cyber "encyclopaedia" of articles promoting terrorism, including discussion of plans to set up a secret Islamic state somewhere in Scotland.

Munshi and Khan had lived 10 miles apart. Khan wanted to fulfil the teenager's wish to go abroad and "fight jihad", and during one internet exchange discussed how the schoolboy might smuggle a sword through airport security.

Munshi, whose online Arabic profile "fidadee" means a "person ready to sacrifice themselves for a cause", ran a website selling hunting knives and Islamic flags and was the cell's computer specialist. Two bags of ball-bearings - the shrapnel of choice for suicide bombers - were found in one of his pockets. The teenager, whose grandfather is Sheikh Yakub Munshi, president of the Islamic Research Institute of Great Britain at the Markazi Mosque, Dewsbury, also stored notes on martyrdom under his bed.

"One who is not taking part in the battle nor has the sheer intention to die is in the branch of hypocrisy," they read.

Khan, the schoolboy's mentor, had links with proscribed terrorist organisations Jaishe-Mohammed and Lashkar-e-Tayyaba. Khan's encyclopaedia included US and Canadian military training manuals, a Terrorist's Handbook, a Mujahideen Explosives Handbook, and a Mujahideen Poisons Handbook, containing a recipe for ricin, the gas used in the Tokyo subway attacks. It also spoke of encouraging "brothers" to experiment on "kuffar", non-believers.

Khan - Del Boy to his contacts - ran At-Tibiyan Publications, an "online extremist support network".

In one exchange he spoke of finding a "big target and taking it out ... like a military base in the UK".

Khan and Munshi both blamed "curiosity" for their hoard of extremist materials. A third defendant, post office night sorter Sultan Muhammad, 23, who is Khan's cousin and was said to be his "right-hand man", was also convicted of terror offences. A fourth, Ahmed Sulieman, 30, from London, was cleared of three possession allegations after explaining the files found belonged to somebody else.