The PM said at once, leaning forward in her chair, 'That is why I regard it as an act of war. But unfortunately we have not only to put our own personal feelings into the background, Mr Ambassador, but to do all we can to damp down public concern to the minimum.' She leaned back again, resting a slim hand on the arm of her chair. 'It won't be easy.'

The foreign secretary looked at the ambassador. 'You don't think there's even the slightest chance of your president simply saying that unless the Soviets come across with an immediate and generous apology he'll call off the summit meeting?'

'I would like to think so. I do not, however, think so.'

'There's not the slightest chance,' someone said impatiently, 'that they'd apologize anyway. They've denied any blame and they'll go on denying it.'

'Are your people still trying to locate the submarine?'

'Yes. So are NATO investigators. But those waters are within the Arctic Circle and it's midwinter, with rough seas running.'

'Mr Ambassador, if the vessel could be found, would it be possible for divers to see whether it was an explosion on board, as the Soviets claim, or an armed attack that sent it down?'

'I think there's no question of that. But it's academic; I'm told there's almost no chance of the submarine being found, in those conditions.'

'Wouldn't the crew have signalled by radio if the ship had been in some kind of distress?'

'If they could have surfaced to do it, yes. They might not have been able to do that.'

'Do you think it was a depth charge — a warning depth charge the Soviets had in fact dropped but later decided to deny — that sank the submarine?'

Two or three of them looked at the thin man who sat with his legs crossed, tall in the chair. I put him down as Admiralty. 'It would need a great number of depth charges to sink a vessel the size of the SSN Cetacea. Again, the Soviets could have dropped a very great number, without coming anywhere near the target. The boat would have normally surfaced perhaps a couple of times a day to spread her antenna and signal base; in those waters, where in midwinter there's no sunlight at noon, she could have done this quite close to the Russian coast without being seen. In other words, I don't think for a moment that she was unaware of her location at any time; and if the captain had heard one depth charge going off, he would have surfaced — or changed course at once towards the open sea.'

'Can we be sure that the Soviets did in fact detect the presence of the Cetacea off their shores?' The PM.

'Not completely sure, ma'am.' He recrossed his long thin legs. 'But it would have been difficult for them not to. In those waters, very close to their largest naval base at Murmansk, they have underwater listening stations in a very wide array. Transonar-transducers would pick up the presence of an alien vessel easily enough, and relay the information to manned posts. Of the Soviet's six hundred or so active submarines, about four hundred are obsolescent diesel-powered boats used for patrolling the shores of the entire continent of Asia. A good few of these patrol the Barents Sea, to protect Murmansk, and they could well have picked up the noise of the Cetacea. They would-'

'But with all their own submarines around, how could they distinguish-'

'Every boat makes its own personal kind of noise, and a fast nuclear-powered Los Angeles class submarine sounds vastly different from a Soviet diesel.'

'Could they have known how far off shore the submarine was?'

'You mean whether it was beyond the twelve-mile limit, ma'am?'

'Precisely.'

'They would have had a fair estimation. I wouldn't go further than that.'

'Do you think, Admiral, that the Soviets attacked and sank the submarine?'

The silence came in like a Shockwave.

I watched the prime minister. She was leaning forward again, not taking her eyes off the admiral. He was studying his thin veined hands, giving himself time; but he didn't need very long. 'Yes, Madam Prime Minister, I believe they attacked and sank it.'

'Without warning?'

'We can't even guess at that. There were no survivors. Only the Soviets know.'

'Wouldn't it have been to their advantage to warn the submarine before attacking, to avoid a grave international incident?'

The admiral uncrossed his legs and got up stiffly. 'If you'll excuse me, I need to stretch a little-'

'Of course-'

'Thank you.' He took a pace or two, his hands tucked behind him. 'I would have thought, yes, that they would have warned the boat first, if they'd given themselves time to consider.'

'Do you see any parallel-' this was the US ambassador now — 'between this act and the downing of the Korean airliner?'

'Several. But the aspect common to both acts is unfortunately that we in the West haven't got full information.'

'No survivors.'

'Quite.' The admiral took another turn across the Persian carpet. 'I should point out that although we might regard the sinking of the Cetacea as an act of war, the Soviets might claim with equal justification that the presence of a NATO submarine in their waters and within the proximity of their major naval base is also an act of war.'

'But they don't claim that.'

'Not at present. Their line at present is simply that they had no knowledge of the Cetacea until the Norwegian coastguard sighted debris drifting from the east.'

'That's typical of them,' said the Foreign Secretary, and got up too. 'If you don't mind, Madam Prime Minister-'

'We should move about, of course. This is going to be a long session, gentlemen.'

'Typically,' Cranley went on, 'they start out by denying everything in a case like this. It gives them time to think, and avoids the risk of putting their foot in their mouth. Today they're saying that the submarine must have exploded of its own accord. Tomorrow they'll start screaming that it shouldn't have been in their waters anyway.'

The PM was still in her chair, and I watched her, not getting up like most of them. I hadn't got the drift yet. I couldn't see why Britain was so involved as to call a high-level meeting in Downing Street. Or why the Bureau was involved.

'Wouldn't you say, Admiral Cummings, that a major incident like this, entailing the loss of more than a hundred lives and a nuclear submarine, would come under the terms of the Incidents at Sea Treaty we all signed with the Soviets in 1972?'

'Oh yes. I tried to telephone Admiral Novoselov in Moscow as soon as I heard the news of the sinking, but they told me he was unavailable. That's unusual.'

'In the case of the aircraft carrier Kitty Hawk,' said the US ambassador, 'our people were able to contact Novoselov immediately.'

'There's not so much in common, Mr Ambassador, with the two incidents. True, the damage to your carrier by the Soviet submarine was in the region of two million dollars; but the collision occurred in international waters in broad daylight, and was the obvious result of poor seamanship on their part.

Also there was no loss of life. In the present case we have a death toll of one hundred and five sailors on active duty and the presence of a NATO submarine in waters close to the Soviets' major naval base. With the Kitty Hawk there were a few red faces and the dismissal of one Soviet submarine commander. With the Cetacea, we already have your president's declaration of a national day of mourning throughout the United States of America.'

The PM got up at last, and took an elegant step across to the fireplace, standing with her back to it. The central heating was having a job to cope with the winter temperatures outside; from where I was sitting I could feel a cutting draught coming through a gap in the curtains.

'Let me ask you, Admiral, whether you've reached any kind of construction, in your own mind, of what actually happened in the Barents Sea four days ago. Perhaps that's not quite a fair question, but it's an important one.' In a moment she added: 'You don't have to commit yourself, of course.'