To Liz’s acute irritation Mackay pronounced the Islamic names in such a way as to make it abundantly clear that he was an Arabic speaker. Just what was it with these people? she wondered. Why did they all think they were T. E. Lawrence, or Ralph Fiennes in The English Patient? A complicit flicker from Wetherby told her that he shared her sentiments on the matter.

“Our feeling at Vauxhall is that this activity is significant,” continued Mackay urbanely. “Two reasons. One: al Safa’s principal role is as a bag man, moving cash between Riyadh and the Asian terror groups. If he’s on the move, then something nasty’s in the pipeline. Two: the Children of Heaven are one of the few ITS groups thought to have included Caucasians in their ranks. A Pakistani Intelligence Service surveillance report from about six months ago indicated the presence in the camp of, and I quote, ‘two, perhaps three individuals of identifiably Western appearance.’ ”

He extended spatulate, sun-browned fingers on the table in front of him. “Our concern-and we’ve communicated this over the weekend to all stations-is that the opposition may be about to deploy an invisible.”

He let the remark hang for a moment. The calculated theatricality of his delivery did not lessen the impact of his statement. An “invisible” was CIA-speak for the ultimate intelligence nightmare: the terrorist who, because he or she is an ethnic native of the target country, can cross its borders unchecked, move around that country unquestioned, and infiltrate its institutions with ease. An invisible was the worst possible news.

“That being the case,” Mackay continued smoothly, “we would suggest that Immigration be brought into the loop.”

The Home Office man frowned. “What’s your view on likely targets and the timing of all this? We should probably up the security status of all government buildings from black to red, but that causes administrative problems, and I don’t want to move on it too soon.”