Iraq strikes: Pure symbolism or precursor to Syria?

Media playback is unsupported on your device
Media captionMr Cameron's hands shook as he told MPs military action was his and their duty, reports Nick Robinson

Six RAF Tornado strike aircraft will once again be in action over the skies of Iraq very soon - in theory as early as this evening but I understand that Saturday night is more likely.

The question today's Commons vote leaves unanswered is whether these attacks will mark the start of the third Iraq war in the past quarter of a century or what Ken Clarke today called a largely symbolic contribution to the coalition which is already attacking the forces of the so-called "Islamic State".

The RAF's promised contribution is modest by historical standards - three times as many planes flew over Libya - and other Western countries - the French, Dutch, Belgians, Danish and Australians - have committed as many or more fighters.

However, what will worry opponents of military action and those who are sceptical about it is the prime minister's clear desire to extend action to Syria. He has promised MPs another vote before that happens unless there is a need to move swiftly to avert a humanitarian catastrophe.

The Labour leadership have signalled their concerns about extending air strikes to Syria but have not expressed outright opposition.

One well-placed government source told me that what he called "the next step" would be possible if people saw the success of action in Iraq or if IS carried out further murderous attacks on hostages, or targets in Europe.