Britain’s youngest convicted terrorist was sentenced to two years in a young offender institution yesterday.

Hammaad Munshi, from Dewsbury, West Yorkshire, was 15 when he was recruited into a worldwide plot to wipe out non-Muslims.

He was arrested in 2006 after police found material promoting “murder and destruction”, including a guide to making napalm, on his computer and under his bed. Now 18, he was convicted of making a record of information likely to be used for terrorist purposes.

Munshi, a GCSE student and grandson of a leading Islamic scholar, led a double life, obediently attending school by day and surfing jihadist websites at night. He was part of a cell of cyber groomers devoted to brainwashing the vulnerable into killing “kuffar”, or non-believers. The court was told that he wished to become a martyr.

Sentencing the teenager yesterday at the Old Bailey, Judge Timothy Pontius said that he had given Munshi a lighter sentence because the boy had fallen “under the spell of fanatical extremists” who took advantage of his naivety.

The judge added: “There is no doubt that you knew what you were doing.” He said that the nature of what Munshi downloaded, including a document called How to Make Napalm, made it a “particularly serious offence”.

He told Munshi: “You have brought very great shame upon yourself, your family and your religion.

“However, in the light of the evidence, I have no doubt at all that you, amongst others of similar immaturity and vulnerability, fell under the spell of fanatical extremists, and your codefendant Aabid Khan in particular.

“They took advantage of your youthful naivety in order to indoctrinate you with pernicious and warped ideas masquerading as altruistic religious zeal. Were it not for Aabid Khan’s malign influence, I doubt this offence would ever have been committed.”

The judge said that he took into account Munshi’s age, but added: “It is plainly a case where deterrence must be in the forefront of the court’s mind.” Harendra de Silva, QC, for the defence, said that the student had been subjected to “grooming and manipulation” by others who were “more criminally inclined”.

During his trial, Blackfriars Crown Court was told that he downloaded files about making napalm, detonators and grenades for himself, Khan and Sultan Muhammad. The student was desperate to go abroad and fight and had internet discussions with Khan about how to smuggle a sword past airport security.

Munshi ran a website selling hunting knives and Islamic flags and had the online profile “fidadee”, meaning a “person ready to sacrifice himself”. He was arrested in 2006 as he made his way home from school.

In a statement on behalf of Munshi’s family, his grandfather said: “As a family we have always tried to abide by and uphold the laws of the United Kingdom of which we are proud to be citizens. We respect, therefore, today’s judgment. But like any other family in this country, we are deeply upset by the situation in which Hammaad finds himself. The past 2½ years have been stressful, not only for him and our family, but also for the whole community in Saville Town. All of us feel there are lessons to be learnt, not only for us, but also for the whole Muslim community in this country. This case demonstrates how a young impressionable teenager can be groomed so easily through the internet to associate with those whose views run contrary to true Muslim beliefs and values.”

Khan, 23, of Undercliffe, Bradford, was jailed for 12 years on three counts of possessing articles for terrorism.

Muhammad, 23, of Manningham, Bradford, was given ten years for three similar charges and one of compiling information for terror.

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