There is no such thing, we older hands like to say, as an intelligence operation that does not occasionally run to farce. The bigger the operation, the bigger the belly laughs, and it is a matter of Service history that the week-long manhunt for Bartholomew alias Barley Scott Blair generated enough frenzy and frustration to power a dozen secret networks. Orthodox young novices like Brock from the Russia House learned to hate Barley's life before they even found the man who led it.

After five days of chasing after him, they thought they knew everything about Barley except where he was. They knew his free-thinking parentage and his expensive education, both wasted, and the unedifying details of his marriages, all broken. They knew the café in Camden Town where he played his chess with any layabout spirit who happened to drift in. A regular gentleman, even if he was the guilty party, they told Wicklow, who was posing as a divorce agent. Under the usual tacky but effective pretexts, they had doorstepped a sister in Hove who despaired of him, tradesmen in Hampstead who were writing to him, a married daughter in Grantham who adored him and a grey-wolf son in the City who was so withdrawn he might have taken a vow of silence.

They had talked to members of a scratch jazz band for whom he had occasionally played saxophone, to the almoner at the hospital where he was enrolled as a visitor and to the vicar at the Kentish Town church where to everyone's amazement he sang tenor. 'Such a lovely voice when he shows up,' said the vicar indulgently. But when they tried, with old Palfrey's help again, to tap his phone to get more of this lovely voice, there was nothing to tap because he hadn't paid his bill.

They even found a trace on him in our own records. Or rather the Americans found it for them, which did not add to their enchantment. For it turned out that in the early 'sixties, when any Englishman who had the misfortune to possess a double-barrelled name was in danger of being recruited to the Secret Service, Barley's had been passed to New York for vetting under some partially observed bilateral security treaty. Furious, Brock checked again with Central Registry who, after first denying all knowledge of Barley, dug up his card from a cut in the white index that was still waiting to be transferred to the computer. And from the white card, behold a white file containing the original vetting form and correspondence. Brock rushed into Ned's room as if he had found the clue to everything. Age, 22! Hobbies, theatre and music! Sports, nil! Reasons for considering him, a cousin named Lionel in the Life Guards!

The payoff alone was lacking. The recruiting officer had lunched Barley at the Athenaeum and stamped his file 'No Further Action', taking the trouble to add the word 'ever' in his own hand.

Nevertheless this quaint episode of more than twenty years ago had a certain oblique effect on their attitude towards him, just as -they had puzzled uneasily for a while over the bizarre left-wing attachments of old Salisbury Blair, his father. It undermined Barley's independence in their eyes. Not in Ned's, for Ned was made of stronger stuff. But in the others, Brock and the younger ones. It led them to feel they owned him somehow, if only as the unsuccessful aspirant to their mystique.

A further frustration was provided by Barley's disgraceful car, which the police found parked illegally in Lexham Gardens with the offside wing bashed in and the licence out of date and a half bottle of Scotch stuck in the glove compartment with a sheaf of love letters in Barley's hand. Neighbours had been complaining about it for weeks.'

'Tow it, boot it, charge it or just crush it?' the obliging superintendent of traffic asked Ned over the phone. '

'Forget it,' Ned replied wearily. Nevertheless he and Brock hastened round there in the vain hope of a clue. The love letters turned out to have been written to a lady of the Gardens but she had given them back to him. She was the last person in the world, she assured them with a tragic air, to know where Barley was now.

It wasn't till the following Thursday, when Ned was patiently checking Barley's monthly bank statements, that he discovered among the overdrawn columns a quarterly standing order in favour of a property company in Lisbon, a hundred and something pounds to Real Somebody Limitada. He stared at it unbelievingly. He kept staring. Then he said a foul word where normally he never swore. Then he. phoned Travel in a hurry and had them check old flight lists from Gatwick and Heathrow. When Travel phoned back, Ned swore again. They were home. Days of phone calls, interviews and banging on doors, the rules bent in all directions, watch lists, cables to friendly liaison services in half the capitals of the world, their vaunted Records Section humiliated in front of the Americans. Yet nobody they had spoken to and no researches had revealed the one crucial,. indispensable, idiotic fact they needed to know: that ten years ago on a whim Barley Blair, having inherited a stray couple of thousand from a remote aunt, bought himself a scruffy pied-A-terre in Lisbon, where he was accustomed to take periodic rests from the burden of his many-sided soul. It could have been Cornwall, it could have been Provence or Timbuktu. But Lisbon by an accident had got him, down on the waterfront, next to a bit of rough parkland, and too near the fish market for a lot of, people's sensitivities.

An embattled calm settled over the Russia House with this discovery and Brock's bony face took on a sallow fury.

'Who's our Brother Lisbon these days?' Ned asked him, light as a summer breeze once more.

Then he telephoned old Palfrey alias Harry and put him on permanent standby which, as Hannah would have said, described my situation nicely.

Barley was sitting at the bar when Merridew walked in on him. He was perched on a stool and shooting his mouth off about human nature to a drink-sodden expatriate major of artillery named Graves: Major Arthur Winslow Graves, later whitelisted as a Barley contact, his only claim on history and he never knew it. Barley's long pliant back was arched away from the open door and the door led off the courtyard, so Merridew, who was a fat boy of thirty, was able to collect some much needed breath before he made his pitch. He had been chasing Barley half the day, missing him everywhere and getting more furious with each rebuff.

At Barley's flat, not five minutes' walk from here, where an Englishwoman with a common accent had told him through the letterbox to get stuffed.

At the British Library, where the lady librarian had reported that Barley had spent an afternoon browsing, by which she appeared to imply - though promptly denied it when directly asked that he was in an alcoholic stupor.

And at a revolting Tudor tavern in Estoril, where Barley and friends had enjoyed a liquid supper under plastic muskets and noisily departed not half an hour before.

The hotel – it prefers to call itself a humble pensão – was an old convent, a place the English loved. To reach it Merridew had to scale a cobbled stairway overhung with vines and, having scaled it and taken a first cautious look, he had to hurry down it again in order to tell Brock to run, 'and I mean really run,' and telephone Ned from the café on the corner. Then scale it yet again, which was why he was feeling so puffed and even more than usually put-upon. Smells of cool sandstone and fresh-ground coffee mingled with the night plants. Merridew was impervious to them. He lacked breath. The sob of distant trams and the honking of boats provided the only background sounds to Barley's monologue. Merridew had no awareness of them.

'Blind children cannot chew , Gravey, my dear old charmer,' Barley was explaining patiently while he rested the point of his spidery forefinger on the major's navel and his elbow on the bar beside an unfinished game of chess. 'Fact of science, Gravey. Blind children have to be taught to bite. Come here. Close your eyes.'

Tenderly taking hold of the major's head in both his hands, Barley guided it towards him, parted the unresisting jaws, and popped in a couple of cashews. 'There's a lad. On the command champ, champ. Mind your tongue. Champ. Repeat.'

Taking this as his cue Merridew hoisted his hail-fellow smile and ventured a step into the bar, where he was surprised by two life-sized carvings of mulatto ladies in court dress standing either side of him at the doorway. Colour of hair chestnut, colour of eyes green, he rehearsed, checking off Barley's points as if he were a horse. Height six foot nothing, clean-shaven, well-spoken, slender build, idiosyncratic dress. Idiosyncratic, my foot, thought tubby Merridew, still winded, while he examined Barley's linen. bush-jacket, grey flannels and sandals. What do the fools in London expect him to wear on a hot night in Lisbon? Mink?

'Ah, excuse me,' Merridew said pleasingly. 'I'm actually looking for someone. I wonder if you can help me.'

'Which proves, my dear old mother's arse,' Barley resumed, when he had carefully restored the major to an upright position, 'quoting the celebrated song, that notwithstanding the fact that the big juju man made us of meat, eating people is wrong.'

'I say, do pardon me, but I rather think you're Mr. Bartholomew Scott Blair,' said Merridew. 'Yes? Correct?'

Keeping a grasp upon the major's lapel in order to avert a military disaster, Barley cautiously turned himself half-circle on his stool and looked Merridew over, beginning with his shoes and ending with his smile.

'My name's Merridew from the Embassy, you see. Only I'm the Commercial Second Secretary here. I'm frightfully sorry. We've received a rather pressing telegram for you over our link. We think you should pop round and read it straight away. Would you mind?'

Then unwisely Merridew permitted himself a mannerism peculiar to plump officials. He flung an arm out, cupped his hand and passed it officiously over the top of his head as if to confirm that his hair and his cover were still in their proper places. And this- large gesture, performed by a fat man in a low room, seemed to raise fears in Barley that might otherwise have slumbered, for he became disconcertingly sober.

'Are you telling me somebody's dead, old boy?' he asked with a smile so tense it looked ready for the worst of jokes.

'Oh my dear sir. Don't be so Gothic, please. It's a commercial thing, not consular. Why else would it come over our link?' He tried a placatory giggle.

But Barley had not yielded. Not by an inch. He was still looking into the pit, wherever Merridew might choose to look himself. 'So what the hell are we telling ourselves, actually?' he asked.