The father of Fusilier Lee Rigby has said he wants an apology from Britain's intelligence services after accusing them of failing to prevent his son's murder.
The Intelligence and Security Committee said in a report that spy agencies could not have stopped the soldier's murder in May 2013, despite his killers featuring in a total of seven error-filled operations before the attack.
Facebook hosted an exchange between Michael Adebowale and an overseas extremist ahead of the murder of Lee Rigby, ITV News understands.
In the exchange Adebowale spoke of his intent to murder a soldier.
In a statement, a spokeswoman for Facebook said they took "steps" to prevent people using the site for terrorist purposes.
Lee Rigby's stepdad and sister criticised social media companies for failing to notify the authorities of users plotting a terror attack.
ITV's UK Editor Rohit Kachroo looks at the findings of a report into the extent of intelligence agencies' knowledge of Lee Rigby's killers