British firepower would be effective if we were prepared to deploy sufficient military force.

Sir, Michael Fallon, the defence secretary, is correct to call the lack of RAF airstrikes against Isil in Syria “morally indefensible”.

Last week the House of Commons foreign affairs committee recommended no extension of British military action into Syria “unless there is a coherent international strategy that has a realistic chance of defeating Isil and of ending the civil war in Syria”.

Given the complexity of the situation on the ground and the rival interests of the parties, such a strategy will be a long time in the making. In the meantime, Isil [Isis] will continue to slaughter the innocent, obliterate history, attract the gullible and multiply refugees.

Since the committee did not condemn the US, Australia and France for hitting targets in Syria, it seems to think that someone needs to. But if someone, why not Britain?

Because, it says, British firepower would have nothing but “a marginal effect”. That surely depends on how much military force we decide to deploy, which depends in turn on how important we think it is to destroy Isil. Committee witnesses were in no doubt that it poses “a major threat to the UK”.

Besides, as a permanent member of the UN Security Council, Britain carries a special responsibility to use force in public international service, when needed. And, as the report itself admits, our allies would prefer us not to make them carry the can alone.

Britain really can, and should, do two things at once: negotiate a coherent international strategy while striking Isil at its Syrian roots.