‘But why return to that regime?’ said Dyer. ‘They’ve imprisoned his baby daughter. And possibly tortured his wife.’

‘Which might indicate that he has made a significant breakthrough …’

‘To bargain for their release?’ Updark slid in.

‘If he’s missing, isn’t it more likely the Iranians have got to him already?’

‘That is what we’re looking into. If the Mullahs did believe that one of their own scientists had landed this whale of a fish in Oxford which would give them hegemony over all other nations, and yet hadn’t whispered a word of it to his superiors, then the suspicion of extreme conservative hardliners would be boundless. Not much space for dissent in that lot.’

‘He might have been abducted by the Al-Quds Force is what we’re thinking,’ said Hissop.

‘They’re like Augustus’s Praetorian Guard,’ explained Updark. ‘I’m sure you remember your Classics – the best, most loyal legionnaires chosen to protect the Emperor, only in this case the Ayatollah. One of their jobs is to liquidate his opponents abroad. Before the treaty, they were responsible for a spate of assassinations.’

‘So what are you saying? Rustum could be dead?’

‘Could be,’ said Updark. ‘Abduction is more likely, though – so that he can reveal to the Mullahs every last iota of his secret.’

Hissop was studying his clipboard. ‘Since early this morning we’ve been hunting a white delivery van registered in Cowley. A CCTV camera in Norham Gardens caught three bearded Asian-looking men bundling into the back a sofa-sized object which seemed to be missing its cushions.’

‘In other words, it might not have been a sofa,’ said Updark.

‘But what if it was a sofa?’ objected Dyer. ‘And what if it’s not the Iranians who’ve snatched him? What if someone else got there first?’

‘Anyone in mind?’ asked Updark.

‘You said yourself there might be a lot of people after him.’

‘What they’re all after,’ said Updark, pronouncing each word meticulously as if he were unpacking his sponge bag and arranging hairbrushes on a dresser, ‘is his knowledge of how he might have done whatever it is he might have done. As, I should add, John, are we. I can’t tell you what his contraption looks like, whether it resembles an omnibus or a blunderbuss, but already I’ve got the cuckoos in London saying: “We’ve got to have one of these. British flag on top.” This is the position likely to be adopted as well in Tel Aviv and Riyadh and Beijing. And indeed also by Mr Putin.’

Hissop said: ‘Moscow has its own secret programme of scientists working on fusion, but if something interesting is happening in Russia we won’t know until it’s very late.’

Dyer thought of the nervous way that Marvar had eyed the cars parked in Great Clarendon Road. ‘He was terrified that he was being watched …’