It was nearly three years ago now that we saw some unforgettable photographs in the media: the body of the little boy lying face down on the Turkish beach and the long line of refugees walking through the wheat fields of Eastern Europe.

It was the images we didn’t see which worried me most: those of the very young and very old who couldn’t leave home to walk across Europe. As the conflict in Syria continues we see new pictures: the photographs of innocent people suffocating in chemical attacks in Douma and barrel bombs repeatedly used on medical facilities....