A man who stored up what police called a "vast library of terrorist material" has been jailed for nine years.
Police said they were unsure who Altimimi really was
Omar Altimimi, of Bolton, was convicted at Manchester Crown Court of six charges of possession of material for a purpose connected with terrorism.
Recorder of Manchester, Judge Maddison, said Altimimi, 37, was "a sleeper for some sort of terrorist organisation".
Passing sentence, he added: "It is not known when, if and how you might have been called upon to play your part."
Altimimi hoarded manuals on how to set up a terror cell and carry out bombings, and had identified night clubs and airports among "suitable targets".
He had denied all knowledge of the material found on his computer and had pleaded not guilty to the charges.
Judge Maddison added: "The offences, contrary to the Terrorism Act, are, in my view, of the most serious of their kind likely to come before the court.
"A person convicted of terrorist offences must expect a substantial sentence."
He was also convicted of two charges under the 2002 Proceeds of Crime Act.
Yusuf Abdullah, 30, was also sentenced on Friday and was given a three-year jail term for proceeds of crime offences.
Police arrested Abdullah, also of Bolton, at the same time as Altimimi. He earlier pleaded guilty to acquiring $54,610 (£27,213) of criminal property.
'Range of identities'
During his four-week trial, the jury heard how Altimimi had arrived in the UK from the Netherlands in 2004.
Prosecutors said Altimimi created three identities and was collecting terror information on his computer.
The jury convicted him of possessing files relating to an organisational chart for a terror cell, instructions on bomb detonators, instructions on making explosives, and details about chemical explosives and "bombing strategies".
The father-of-three was arrested last year on suspicion of money laundering when he tried to withdraw £3,000 believed to have been stolen from the Yemen Tourist Promotion Board.
The prosecution said the computer carrying terror-related files was recovered from Altimimi's home when it was raided seven weeks after his arrest.
Detective Chief Superintendent Tony Porter, head of the Greater Manchester Police Counter Terrorism Unit, said Altimimi "developed a range of identities, which would allow him to expand his terrorist activities".
Altimimi used his wife and children to appear as an ordinary family man and blend into the community, he said.
"But behind closed doors he was downloading shocking videos of executions, bomb-making recipes and information on how to establish a terrorist cell," Det Ch Spt Porter added.
He added: "We will never know exactly what Altimimi was preparing to do but it was clear he had support and links with terrorists across the world."
Greater Manchester Police (GMP) revealed that when Altimimi's two computers were seized other material found included a job description for a role with GMP police and application forms for Bolton Council and for a teacher training position.