'Lothar was clever then, in not opening his mouth too wide. The doorkeeper must assume that you know your own stock, and he might have thought it fishy if Lothar, whom he took to be you, had asked for a greater number than there happened to be available. I take it, too, that quite a small part of what he's got would be sufficient for him to have the stuff analysed, and after that there would be no limit to the quantity that could be made up?'

'The analysis would take time, and they might not get the formula exactly; but near enough. And the Russians have many clever chemists, so they might even improve on it.'

'How often do you send consignments up to Scotland?'

'As required; but, on average, about once every three weeks. We send larger consignments now to Australia for the I.C.B.M. range there, but less frequently.'

By this time they were approaching the air strip. The aircraft that had taken the American up to Farnborough that morning, and since returned to collect C.B. and Barney, stood at one end of it; but evidently Forsby had not yet succeeded in getting hold of the pilot, as there was no sign of life. Neither was there any sign of life near the two hangars, in the control tower or at the building that housed the small ground staff. Barney drove up to the latter and they got out.

The building contained only an office and off-duty room on the ground floor and a dormitory for half-a-dozen men above. Verney hurried into the office, found it deserted, then crossed the passage and strode into the room opposite. An R.A.F. Corporal was lounging there with his feet up, reading a Sunday paper. Verney addressed him sharply.

'I am a colleague of Squadron-Leader Forsby's. Are you the duty N.C.O.?'

'Yes, Sir.' The corporal replied, coming quickly to his feet and switching off the radio.

'I understand that about half past two an aircraft came in and took off about half an hour later.'

'That's right, Sir,' the man confirmed their worst fears. 'Quite unexpected it was. Usually we are warned in advance and given the E.T.A. in ample time for whichever of us is on duty to get hold of the others and man the control tower. But with good weather, like it is today, and the strip clear that isn't really necessary. All the same, it's against regulations, and I was a bit took aback.'

'What did you do?'

'I walked over, Sir, and had a word with the pilot. He said that he had come down from our I.C.B.M. Station in the Hebrides to pick up some stuff that was wanted urgent, and he couldn't understand why they had failed to send us a signal about him.'

'What did you do then?'