Scotland Yard has won a court order to force Channel 4 to hand over unbroadcast footage of an interview with an Islamic extremist.
Officers want to study previously unseen material gathered for the channel’s documentary Dispatches: Britain Under Attack broadcast on August 6.
It is understood they are looking for evidence of criminal offences such as inciting terrorism, made illegal by the Terrorism Act 2000.
The programme featured a disguised man, known as Abu Muhammed, who said the July 7 bombings were justified and told British Muslims they were in a state of war.
He said: “It was very justified. Because Allah says if someone committed an aggression against you, you commit aggression against them. If somebody transgresses against you, transgress against them the same way.”
According to the programme, Muhammed is banned from entering Britain but broadcasts to British Muslims via the internet.
The Metropolitan Police force was granted a limited production order at the Old Bailey, a Channel 4 spokeswoman said.
She added: “The police confirmed in court that the subject of their investigation is the radical cleric Abu Mohammed, not Channel 4. Channel 4 will comply with the terms of the order.”