Her lights resembled a fishing boat's and I didn't recognize her until the tender began slowing, then the configuration came up in silhouette against the lights of the Kowloon shoreline: radar mast, conning-tower, diving planes. The sea was glass calm.

The lifeline was still rigged on deck but a couple of hands started bringing it in as we went on board. There were two or three figures standing on the bridge and Ferris peered at them in the inadequate light.

'Wing,' he said, 'this is Bill Ackroyd, captain.'

We said hello and a seaman reached down and took my stuff from the man in the tender. One of the air bottles banged against a stanchion and someone said, 'Easy now .. .' I looked down.

'Careful with that bag there - it's fragile. 'Ay ay, sir.'

It was the short-wave Hammerlund transceiver Ferris had dug up for me and we'd put it in a waterproof bag along with the lamp and the rations.

People were speaking in low voices and I noticed the main bridge lights were shrouded: except for her riding lights Swordfish was in wartime' rig. The tender backed off and swung in a wide curve away from us, leaving a scimitar of iridescent light across the sea. I could feel the vibration of the diesels under my feet.

'What's that over there?' I asked Ferris. It looked like some kind of launch, standing off at a hundred yards.

'Escort,' the skipper said.

'For the whole trip?'

'Just out of harbour. Would you like a drink?'

He took us below.

There was gin set up in the wardroom and I asked for a straight tonic and Ferris wanted to know if they had any milk and Ackroyd began looking at us as if we were a couple of freak sea-anemones they'd dragged up with the anchor chain.

'Frank Topper,' he said close to the chest. 'Diving officer.'

We all said hello again and I wished to Christ we could cut out the garden party and get moving. Ferris had a nervous smile switched on against any doubts in his mind and I began feeling bloody annoyed because my left hand should have had some kind of treatment and I was still in mild aftershock from the station wagon thing and London was pitching us right into a crash-access operation and that meant something had come up on the board and they'd started to panic.

'Cheers,' one of the officers said.

There seemed to be a lot of noise from the fans and blowers but nobody took any notice. Then there was the slam of a steel hatch and two seamen came down and disappeared through a doorway and Ackroyd took us back into the control room. The helmsman was in his seat and there were needles crawling all over the dials and Ferris stood there watching everything with his bright glass eyes and a ruff of hair sticking out where he'd brushed his head on the companionway coming down. Everything had suddenly gone quiet.

'All right,' Ackroyd said. 'Slow ahead both.'

There wasn't any appreciable movement but the bug started glowing across the chart on the DRT and in ten minutes we were out of the harbour. Five minutes later there was another sudden period of inactivity and Ackroyd said:

'Pull out the plug and ease her down to periscope depth.'

The deck began sloping by degrees and I looked at the instruments.

Time 00.31. Course 220 .

Ferris was watching me and I felt like kicking his teeth in because his stare was critical and I knew that if I showed any signs of nerves or fatigue or anxiety he'd have this ship turned about and taken back into harbour. I didn't like being assessed at this phase of a mission: if I felt incapable of going in or doing a decent job I'd say so, he knew that. Better than Loman, perhaps, or Porterfield: they'd send you into the target zone with your nerves in rags and your eyes out of focus from fatigue if they thought you could finish the course without dropping dead.

'We'll slope off,' Ferris said with a bright smile, 'and do some more chatting.' He led me into the wardroom and we sat down and went over the whole thing again. I got it right at the third go and then he filled me in about the liaison and rendezvous patterns, 'The routine rdv's will be prearranged by radio. Ackroyd says we can't risk coming in closer than a. mile from the rig, so if you can swim that distance you'll navigate by the north star and listen for the call of the sea swallow -I'll play you the tape in a minute. Swordfish will pick you up on the sonar and moved slowly to rendezvous.'

This was typical Ferris: in less than twenty-four hours he'd had the call of the sea swallow put on tape and dug up a radio from the American stores and pushed London to give us a ship through the Navy.

'If you're not in a condition to swim as far as that - or any distance at all - we can do you a straight emergency pick-up through the distress channels and send in a coastguard chopper with a net. If --'

'You can't do --'

'Oh yes we can. It'd expose our hand but if I can get you back alive without blowing the mission that's what I'm going to do.'

I knew he meant it but as I looked at him in the flat white light of the wardroom I wondered whether he'd always been so considerate towards his executives in the field, or whether he was trying to atone for what they'd sent him to do that time in Brussels.

'Can I come in?' The captain was standing in the doorway.

'Of course,' Ferris told him. 'We were just chewing the fat.'

For a submarine skipper Ackroyd looked too young but that might have been partly due to the apple-red glow on his cheeks, which I put down to the gin. His eyes were small and quick and he gave explosive little laughs, trying to cover them by tugging at the creases of his tropical slacks or scratching an ear. He looked about the last man to want to creep about under the sea in the confines of a tin coffin.

'Would you like to know anything about this tub? She's "S" Class, commissioned only last year and built for patrol -got two diesels and all mod cons. She's fast, silent and difficult to detect. Just the job for you, what?' He tugged energetically at his creases.

Through the doorway I could hear the pinging of the sonar transducer above the rush of the blowers. There was almost no vibration from the screws.

'Lucky to find ourselves on board,' said Ferris.

'Don't know about luck,' his small quick eyes glancing from Ferris to me and back, 'I understand you put such a squib under their lordships they haven't come down yet!' He scratched his ear, his cheeks glowing. 'What are you chaps?' leaning forward suddenly and lowering his voice. 'Intelligence wallahs or something? MI5?'

'That's right,' said Ferris. I suppose he thought if Ackroyd had. the impression that MI5 worked overseas he might as well leave it at that: a classic piece of disinformation. 'By the way, do you think they'll use depth-charges?'

Ackroyd's face snapped shut and he looked down at his hands.

'You know, that's why you chaps had so much trouble getting us to help you. If I were to take Swordfish into Chinese waters only a few miles north of here, we'd have depth charges dropped on us. No question at all.' His bright eyes came up and scanned us in a series of flicking glances. 'I mean unless we surfaced and explained our presence or signalled we were in some kind of trouble. Now, they can't do that in international waters. But they might try.' His glance took in the doorway and he began speaking close to his chest again. 'It hasn't escaped their lordships that if we are to drop off a frogman within a mile of an offshore oil rig whose structure is Chinese Republican territory, we might encounter objections - and of the most tangible kind. It wouldn't be legal. But it would be understandable.' His laugh exploded and he tugged busily at the lobe of his ear.

Ferris gave a companionable whinny.

'So it's like that,' he said.

'It's like that, gentlemen.'

'Cross our fingers,' said Ferris, and Ackroyd glanced at him. We could both feel the chill coming out of him, though he'd been trying to deal with it. Ferris was claustrophobic, and the idea of being inside this thing when they dropped depth charges on it wasn't making him feel any better.

'Let me explain,' said the captain. 'If they were worried enough about our presence so close to the rig they might try to blow us out of the water and later claim they did it when we were inside their territorial waters and that we drifted south before we bottomed. They'd have to knock us out at the first shy, or we'd start sending radio messages to the effect that we were being attacked in international waters.' He shrugged with his small pink hands. 'Provided they could drown us to a man before we could use the radio, how could anyone dispute their claim?'

We didn't say anything.

'That is the position, then. Of course I'm going to make every effort to avoid an incident. I have seventy crew on board.' His face went shut again and he looked down at the table. 'For the duration of this voyage, gentlemen, Swordfish has been placed on a war footing.'

'This was our only way in,' said Ferris. 'I'm awfully sorry.'

'Give us something to do. You called on the right people -the Silent Service!' A short burst of laughter while he plucked at his ear.

'What time,' I asked him, 'do we expect to arrive off the rig?'

'Come into the control room.'