"Molecules. The sort you don’t want a bomb-sniffer to find. They were sampled from a particular batch of Semtex that the IRA were heavily invested in. Plastic explosive. Distinctive chemical signature. Still a few tons of it out there, as far as anyone knows. And the card from a digital camera. Photographs of mosques, all over Britain. The dates on the images were a few months old, but not over sell-by, as suggestive evidence goes."