A vulnerable Muslim convert who was persuaded by extremists to attempt a suicide bomb attack was jailed for a minimum of 18 years yesterday.

Nicky Reilly, 22, who has Asperger’s syndrome and a mental age of 10, was described by his lawyer as the “least cunning” person ever to have been charged with terrorism.

He was directed online to build nail bombs, which he tried to set off at the Giraffe restaurant in Exeter in May.

The devices went off prematurely and he was the only person injured. At his trial in October last year Reilly, from Plymouth, Devon, who appeared in court as Mohamad Abdulaziz Rashid Saeed, pleaded guilty to attempted murder and preparing an act of terrorism.

Sentencing him to life imprisonment at the Old Bailey yesterday, Mr Justice Calvert-Smith said that although the attack was “an unsophisticated attempt”, Reilly was a “significant risk” to the public.

After his conviction, counter-terrorism officials said that extremists had taken advantage of his low IQ to groom him.

Reilly, who has an IQ of 83, had first been taken to see a pyschiatrist when he was 9 and tried to take an overdose at 16. Kerim Faud, representing him, said: “He may comfortably be deemed to be the least cunning person ever to have come before this court for this type of offence.”

He is thought to have met British-based Muslim radicals in internet cafés near his council home, which he shared with his mother.

Security sources said that radicals encouraged him to visit internet chat rooms and other websites, where he encountered men based in Pakistan who helped to mould a violent hatred of the West. He discussed with the men what his targets should be and they directed him to bomb-making websites.

In a suicide note left in his home he paid tribute to “Sheikh Osama” (bin Laden) and called on the British and US governments to leave Muslim countries. He said that Western states must withdraw their support of Israel, and that violence would continue until “the wrongs have been righted”.

On May 22 Reilly put his plan into action. He left his home with six bottles in his rucksack filled with paraffin, caustic soda and nails. When he arrived at the Giraffe restaurant he ordered a drink and sat for ten minutes before heading to the lavatory to make the bombs.

Fortunately for the 24 customers and 11 staff in the restaurant and the 20 more people lunching outside, the bombs exploded in the cubicle.

Mr Justice Calvert-Smith said yesterday: “I am quite satisfied that these offences are so serious that only a life sentence is appropriate. This defendant currently represents a significant risk of serious harm to the public.

“The offence of attempted murder is aggravated by the fact that it was long planned, that it had multiple intended victims and was intended to terrorise the population of this country. It was sheer luck or chance that it did not succeed.”

He accepted that the attack was unsophisticated but added: “Those who attempt to commit suicide and in doing so murder other people are almost invariably unsophisticated in many aspects. That lack of sophistication saved many Londoners on July 21, 2005.”

Jacqui Smith, the Home Secretary, said: “This case demonstrates that the threat to the UK from violent extremists remains real and serious.” Reilly was the 86th person to be convicted in a significant terrorist case since 2007, she added.

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