Last week I attended a service at Westminster Abbey to give thanks for the lives of those men and women who have died in the line of duty helping to relieve the needs of others.

Some of them will have died caught in the crossfire of someone else’s war. Others will have been deliberately targeted as part of a strategy to maximise terror. Although James Foley was a journalist rather than a humanitarian aid worker, I place him in the same category, because his life’s work was to inform the world of the horror of conflict.

There will always be monsters that mastermind terror campaigns to achieve some religious or ideological objective. Any number spring to mind: Stalin, Pol Pot, Saddam Hussein, Bin Laden, Abu Bakr al-Baghdadi to name but a few.

Who are their footsoldiers and willing accomplices? I believe it remains the case that the chief recruiting sergeant for terrorism are the refugee camps and other similar situations where the hopelessness of existence is at its starkest. Where there is relentless and grinding poverty, injustice, indignity, corruption and inhumanity.

The news that British men and women are fighting for ISIS in Syria and Iraq, many of them boasting on social media about the brutality of their crimes, raises a question about why young people with prospects, from good homes with respectable families, should behave in this way.

There is nothing new about young men going off to seek adventure in foreign wars, but I think we are dealing with a different phenomenon.

Neither do I believe it fair to put it down to “radicalisation” – by which I presume we mean the adoption of radical political and religious beliefs. There are many wacky religions out there but there is a world of difference between believing, and murdering. There is something singularly grotesque about the reports of our countrymen in Syria and Iraq.

Those hostages who have been ransomed tell of torture, beatings and mock executions by British captors.

I have not watched the video of James Foley’s death. To do so, I believe, is to gratify his killers. What is it about these people that they boast about disgusting crimes? A 22-year-old Londoner, now in Syria with ISIS, has announced she wants to be the first female to behead a westerner. There are plenty of others out there who are keen to publish their fantasies.

A surprising number of these psychopaths turn out to be doctors or medical students, but then the career of Dr Mengele ought to have taught us that the medical profession is not immune to infiltration by monsters.

There are, no doubt, studies which analyse this, but we have to confront the truth that some people enjoy killing.

We are right to invest in turning young people away from radicalisation. We should do all we can to make them advocates of our values of tolerance, liberty and democracy. However, we have to recognise we are faced with a minority of wicked criminals, and confront them appropriately.