IT is just a week since Britain and the US vowed to crush the threat posed by Islamic State (IS).

We do not know if this was the reason why IS killed British aid worker David Haines.

His chances of getting out alive were already slim. He was British, by all accounts he did not have kidnap insurance and the UK Government does not negotiate with terrorists.

The latter point has become a source of controversy and growing discomfort for western politicians.

The US does not negotiate with terrorists and nor do our European allies.

But earlier this year IS unexpectedly released four French and two Spanish hostages. It later emerged the French and Spanish governments had paid a ransom via intermediaries.

Should Britain pay to recover kidnap victims?

The Government’s refusal to negotiate did not stop IS abducting Mr Haines. British and American citizens are targets because of their political value – not their monetary value. Paying ransoms is not the root cause of terrorism.

However, handing money to extremists buys more guns and bombs. It also encourages more kidnappings. A leader of al Qaida boasted recently how much money he made from kidnappings and described them as “a profitable trade and a precious treasure”.

Since 2008, al Qaida has banked more than £70m from ransom payments – and the cost to the West is growing. Ten years ago, the average kidnap demand was £150,000, now it runs into millions.

There are no easy answers to this problem but the non-negotiation tactic will only work if Britain, the US and Europe can hold the line.

David Cameron was right to upbraid our European allies at the Nato conference in Wales recently. A united front against IS is the only answer to such savagery.