Evidence heard at Arena public inquiry showed humanity at its best and worst, chairman says as he addresses victims' families

Evidence heard at the Manchester Arena public inquiry has shown humanity both at its worst and at its best, the chairman said as he addressed families to mark the publication of his third and final report.

Sir John Saunders spoke movingly of an 'appalling loss which was so unnecessary' as he paid tribute to the 22 lives lost.

And he said that he 'can only hope that we achieve something by our efforts' - as he confirmed he found a 'significant missed opportunity to take action that might have prevented the attack'.

READ MORE: MI5 'missed significant opportunity' to stop Arena bomber - latest updates

The security service MI5, he said, didn't act swiftly enough over two crucial pieces of intelligence that were not passed on to police.

"It is not possible to reach any conclusion on the balance of probabilities or to any other evidential standard as to whether the attack would have been prevented," he said.

"However, there was a realistic possibility that actionable intelligence could have been obtained which might have led to actions preventing the attack.

"The reasons for this missed opportunity included a failure by the security service, in my view, to act swiftly enough."

Sir John said he was ‘satisfied’ the Abedi brothers used an instruction video placed on the Internet by Islamic State to create the bomb.

And he said more needs to be done to ensure ‘instructions for murder’ are not put up online.

The evidence as a whole, said Sir John, had often been 'gruelling and distressing to listen to'.

"For example, the evidence of people who were there and did their best to help, who will be affected for the rest of their lives by what they saw and heard; the evidence of the bereaved families of the effect that the deaths