A Briton was sentenced to 3-1/2 years in jail on Tuesday for possessing terrorism-related documents that the judge described as "fundamentalist trash".

Yassin Nassari, 28, was convicted last Friday while his Dutch wife Bouchra El-Hor walked free after the jury rejected evidence purporting to show she had urged him to become a "martyr" for Islam.

The charges against Nassari related to files on the hard drive of his computer, including plans for building a missile and extensive material on jihad, or holy war.

"You have somehow been indoctrinated into (these) beliefs, some of which support the use of terrorism by others. I have no doubt you wished to be immersed in this sort of fundamentalist trash," Judge Gerald Gordon told him.

Gordon said there was no indication that anybody would have made "actual terrorist use" of the material.

But the jury's verdict meant that anyone who downloaded such material, whatever their intentions, was at real risk of being convicted under Britain's terrorism laws, the judge said.

"The sooner that is understood, the better."

Nassari will be eligible for parole in around two months, as the time he has already served in prison since his arrest in May 2006 will count towards his sentence. He smiled and gave a thumbs-up sign as he was led away from the dock.

Britain faces what security officials describe as a strong and growing threat from radical Islamists, many of whom cite its role in invading and occupying Iraq as justification for attacks. Nassari was the 16th man convicted and jailed on terrorism-related charges in just over a month.

Peter Clarke, Britain's top counter-terrorism policeman, said that Nassari had the "ideology, ability and determination" to find and download material of use to terrorists.

"He communicated with other like-minded people and shared their interest in gruesome extremist material. He conducted research into how to construct and deploy weaponry commonly used by terrorists in the Middle East," Clarke said in a statement.

While his intentions were unclear, Clarke said, "it is possible that his research could have ended up in the hands of individuals or groups willing to put it into practice."