British MPs will vote later (approx 5pm BST) on whether to take part in air strikes against the Islamic State in Iraq.
The three main Westminster parties all back military action, so it's expected to pass.
The UK government wants authorisation to launch air strikes inside Iraq, but is not pushing for the go-ahead to do the same in Syria.
If the motion passes, the UK's jets could be in action within hours.
It comes after the FBI said it knows the identity of the British man seen in the execution videos of two Americans and a Briton, without giving further details.
Political reporter Theo Usherwood says Parliament is likely to approve military action.
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Crispin Black, former UK intelligence officer, says more details on 'Jihadi John's' identity may follow soon.
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Crispin Black, former UK intelligence officer, says so-called Jihadi John's identity is important.
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Crispin Black, former UK intelligence officer, believes air strikes in Iraq or Syria would be a mistake.
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