I keyed it in: PRETTYMAN, JAMES.'

The machine gurgled before providing a 'Menu' from which I selected BIOG. More soft clattering came from deep inside the machine before Prettyman's twenty-two-page-long service biography came up on the screen. I pushed the control arrow buttons to get to the end of it and found it ended with a summary of Prettyman's last report. This was the standard Civil Service file in which one's immediate superior comments on 'judgement, political sense, power of analysis and foresight' but it didn't say whether Prettyman had retired from the Department or continued to work for it. When I pressed the machine for supplementary material I got the word REVISE.

So I pursued PRETTYMAN J BIOG REVISE and got REFER FILE FO FX MI 123/456, which seemed an unlikely number for a file. I tried to access that file and found ACCESS DENIED ENTER ARCTIC NUMBER.

I couldn't tell the machine the 'Arctic' number it wanted because I didn't even know what an Arctic number was. I looked at my watch. I still had plenty of time to spare before my appointment with Dicky. Dicky had been in a very good mood for the last few days. The Bizet crisis seemed to have faded. There had been no hard news but he told the Department that the Stasi prosecution office were about to release our men because of insufficient evidence and managed to imply that it was all his doing. It was a total fabrication, but when Dicky needed good news he never hesitated to invent some. Once, when I'd tackled him about it, he said it was the only way of getting the old man off his back.

Today Dicky had gone to lunch with his old friend and one-time colleague Henry Tiptree, who'd left his cosy Foreign Office desk for a job with a small merchant bank in the newly deregulated City. Morgan had gone to lunch with them too. Morgan used to be a hatchet man and general factotum for the Director-General but since the D-G's appearances had become fewer and further between, Morgan had nothing to do but pass queries to the Deputy D-G's office and blow smoke at the ceilings of the City's private dining rooms. I suspected that Morgan and Dicky were cautiously investigating their chances of getting one of the six-figure City salaries that I kept reading about in The Economist. In any case, Tiptree, Morgan and Dicky were not likely to finish judging the Havanas and old tawny port until three at the earliest, which is why I'd brought my packet of sandwiches to the Submarine.

So I tried again. I entered the company for which Prettyman worked in Washington. TRANSFER LOAD then PERIMETER SECURITY GUARANTEE TRUST.

The machine purred contentedly and then the screen filled. Here it all was: the address of the headquarters, computed world assets, stock market price and names of president and vice presidents of the PSGT. This wasn't what I wanted so I entered PRETTYMAN into the PSGT queries space. Hiccups. Then I got REFER FILE FO FX MI 123/456.

I went back to REGISTRY ONE and entered that file number. On the screen came the same message as before: ACCESS DENIED ENTER ARCTIC NUMBER. It was a merry-go-round. Had I not been seeking specific information it would not have seemed sinister. Had I not chosen those particular subjects it would not have produced the coincidence.

Now I tried another angle. The data bank held details of departmental employees past and present. I entered the name of my wife SAMSON, FIONA and entered the UPDATE command for the final part of her file.

No surprise now. Up came that damned bogus number that couldn't possibly have come from the normal filing system; REFER FILE FO FX MI 123/456. And of course the subsequent keying was answered by the inevitable request for the ARCTIC NUMBER. So whatever the Arctic number was, it would give an enquirer answers about Jim Prettyman, his US employers – almost certainly a front for some sort of illicit business – and whatever my wife Fiona was doing during those final weeks before her defection.

I went and walked around for a few minutes. Level Three was especially depressing. On one wall the long open room had dark metal shelving packed with spools and huge 12-platter disk packs, and other examples of sophisticated computer software. Another long wall was occupied with the work stations and on the third wall there was a series of desks and soft chairs that were allocated to senior staff. The last wall was of glass, and behind it the toilers came hauling trolleys piled with paper which the machines consumed with terrible appetites.

I stretched my legs and racked my brains. I even drank some of the concoction that the 'beverage dispenser' classified as coffee. I went to the toilet. For many months the question 'Is there intelligent life in the Data Centre?' had been posed in neat handwriting on the wall there. Now someone had scrawled 'Yes but I'm only visiting' below it. The graffito was the only sign of real human life displayed anywhere, for the staff assigned here soon became as robotic as the machines they operated and serviced. I went back to my work station.

I continued for another hour but it was no use. The damned machine always defeated me. In the old days everything was in Registry, and no matter that the flies were grimy, and you had to take your own soap and towel down there, at least if you couldn't find what you wanted there was always someone to show you the bottom shelf where the missing file was put because it was too heavy, or the top shelf where it was put because it was never asked for, or the door it was put against because someone had stolen the wedge that kept the door open. I preferred Registry.

'Where did you have lunch today?' Gloria asked me in that cheerful casual voice that she assumes when suspicion warps her soul. She wasn't visiting her parents this evening: they were at a dentist's convention in Madrid.

'The Submarine,' I said. We were at home and about to have dinner. I was sitting watching the seven o'clock Channel Four news. Gale-force winds were 'lashing the coastline' and bringing 'chaos' and 'havoc' in the way that the weather is apt to do when camera crews have no real news to record. As if to bring the news home to me the window panes rattled and the wind howled loudly through the little trees in the garden. Gloria on her way to the dining room put two glasses of chilled white wine on to the side-table. She was trying to wean me off the hard liquor.

'In the Submarine?' she said with a slight smile and a voice brimming with that malicious one-sided delight for which the Germans coined the word Schadenfreude. 'How perfectly awful!' She laughed.

'Rubber sandwiches from the Dinky Deli,' I added just to complete her pleasure.

'But you weren't back until nearly four,' she called. I could see her in the dining room. She was setting the table for dinner. She did it with the same careful attention she gave to everything. Knives, forks and spoons were aligned with the plastic place-mats; serving spoons guarded the mustard, salt and pepper-mill. The napkins were folded and put into position with mathematical accuracy. Satisfied with the table she came back to where I was sitting, perched herself on the arm of the sofa and took a small sip of her wine.

'I had a meeting at four… with Dicky.' I switched off the TV. It was just a regurgitation of ancient happenings. I suppose the news has to be expanded to fit into its allotted time slot.

'The whole afternoon down there? Whatever were you doing?'

'I stayed on tinkering with the files. I do sometimes.'

'Jim Prettyman?'

She knew me too well. 'That sort of thing,' I admitted.

'Any luck?'

'The same all the time. Have you ever heard of an Arctic coding?'

'No, but there have been a dozen new coding levels in the past year. And there are new top-level data-bank names coming in every month these days.'