(Reuters) – Two Britons were jailed on Friday after being arrested in Hungary where they were suspected of heading to Syria, in breach of strict travel constraints because they had convictions for terrorism offences.

Trevor Brooks, 40, and Simon Keeler, 44, both well-known Islamists, were detained near Hungary’s Romanian border in November having left Britain without informing the British authorities six days earlier.

They were extradited back to Britain and pleaded guilty the following day to breaching notification requirements under counter-terrorism laws. On Friday, they were sentenced for two years in prison at London’s Old Bailey court.

“They’re yet to give us any indication as to why they left the UK and were travelling across Hungary, although clearly our concern is that they may have been trying to get to Syria,” said Detective Chief Superintendent Terri Nicholson.

“We will continue to investigate and if we find any evidence of further offences, then we will look to prosecute.”

Brooks, also known as Abu Izzadeen, is one of Britain’s most high-profile radical Islamist preachers, and rose to prominence in 2006 when he publicly heckled the then Home Secretary (interior minister), John Reid, in front of television cameras.

He and Keeler were jailed for more than four years in 2008 for raising funds for terrorism and inciting people to fight British and U.S. forces in Iraq.

Their jailing comes in a week when Britain’s border checks have come in for heavy criticism over the case of a Briton, now suspected of being an Islamic State executioner, who slipped out of the country despite being on police bail after having been arrested on suspicion of terrorism offences.

Police sent a letter to Siddharta Dhar, suspected of being a masked militant who appears in the latest murder propaganda video from the Islamic State group, asking him to hand over his passport six weeks after he had left for Syria.