The driving, on the other hand, is as Spanish as flamenco and jamón. Cars whipping past at over 160 kph, sliding lane to lane oblivious of sense or reason. It is my habit to copy them, if only because the alternative is a snail-slow crawl in the slipstream of an ageing lorry. Thus I take the Audi well beyond the speed limit, sit on the bumper of the car in front, wait for it to pull to one side, and then surge off into the distance. Traffic police are not a problem. The Guardia Civil tend not to patrol in the long stretches between major towns and one glimpse of my (counterfeit) German driving licence, accompanied by an inability to communicate in Spanish, is usually enough to encourage them to wave me on.

As the weather closes in, however, I am forced to slow down. What had seemed at first like the beginning of a decent, sunny day becomes fogbound and wet, hard rain falling in patches and glistening the road. At this rate it will be four or five hours before I cross the border into the Basque country. A preliminary meeting scheduled in the capital, Vitoria, for one o’clock may have to be postponed or even cancelled. Climbing into the Sierras, I get stuck behind two articulated lorries driving parallel in a macho overtake, and decide to pull over for a coffee rather than sit in the funk of their exhaust. Thankfully, the rain has stopped and the traffic thinned out by the time I rejoin the road, and just after eleven I am passing Burgos. This is where the landscape really comes into its own: rolling, patched fields of green and brown and the distant Cantabrian mountains smashed by a biblical sunlight. At the side of the road, little patches of undecided snow are gradually melting as winter draws to an end. To be away from Madrid, from the pressure and anxiety of Saul, is suddenly liberating.

When the road signs begin to change I know that we have crossed the border. Every town is announced in translation: Vitoria/Gasteiz; San Sebastián/Donostia; Arrasete/Mondragón: government concessions to the demands of Basque nationalism. This is not País Vasco; this is Euskal Herria. Spain is divided into a number of regions with far greater political and social autonomy than, say, devolved Scotland. Under the terms of the constitution hammered out in the aftermath of Franco’s death, the Basques – and the Catalans – were granted the right to form their own regional governments with a president, legislature and supreme court. Everything from housing to agriculture, from education to social security, is organized at a local level. The Basques levy their own taxes, run their own health service – the best in Spain – and even operate an independent police force. As Julian exclaimed over lunch, What more do they fucking want? Explain that in your magnum opus.’

The ‘magnum opus’, as he put it, will probably run to several thousand words, a blend of conjecture, facts and business jargon designed to impress Endiom’s investors and provide a broad overview of the political-financial consequences of investing in the Basque region. ‘Still,’ Julian disclosed, polishing off his second glass of cognac, ‘the idea is to encourage our clients into parting with the readies, yes? No sense in putting them off. No sense at all.’

So, what more do they want? I stop in Vitoria, late for the first of many meetings, and come no closer to an answer. Two hours of employment law and social security benefits with a bespectacled union representative struggling to rein in a bad case of dandruff. It takes twenty-five minutes to find his office and another fifteen for the two of us to walk the damp city streets in search of an eventually mediocre restaurant serving thin soup and stodgy beans. I begin to regret coming. But this is only my second visit to the Basque country and I had forgotten the striking transformation in the landscape as you drive northwest towards the sea, the flat plains of Castilla suddenly soaring into magnificent, bulbous mountains dense with trees and lush grass, the motorway winding frantically along narrow valley floors. This is another country. At half past four I have reached the outskirts of San Sebastián, rain starting to fall and obscuring the hillsides in mist. Every now and again the silhouette of a typical casería, low alpine houses with obtuse angular roofs, will punch through the fog, but otherwise little is visible from the road. So nothing prepares me for the beauty of the city itself, for the long graceful stretch of the Concha, the grandeur of the bridges spanning the Urumea river and the elegance of the broad city streets. Julian’s secretary, Natalia, has booked me into the Londres y de Inglaterra, perhaps the best hotel in town, situated on the seafront looking out over a wide promenade dotted with benches and old men wearing black Basque berets. The promenade is lined by a white iron balustrade and there is no traffic in sight. It would not seem strange for a woman carrying a parasol to pass on the arm of a Spanish gentleman, nor for a child bowling a hoop along the seafront to scurry past in a pair of salmon-pink culottes. I seem to have emerged into a time warp of the fin-de-siècle bourgeoisie, as if the heart of San Sebastián has not changed in over a hundred years, and all of the grim political sparring of the Franco years and beyond has been a myth now happily exploded.

Natalia has reserved a room with a view looking out into the centre of the bay, a perfect natural harbour crowned by a bowl of pristine sand which sweeps in a precise crescent along its southern edge. Even in the cold of February, brave swimmers are inching gingerly out to sea, shivering in the soft breakers rolling in off the Bay of Biscay. I take a shower, write down some notes from the meeting at lunch and fall asleep in front of CNN.

I am woken just after seven by the shrill of the telephone, a call from Julian in Madrid.

‘Forgot something,’ he says, as if we had been in mid-conversation. ‘Meant to say at lunch yesterday, completely slipped my mind.’

‘And what’s that?’

‘I think you should look up an old acquaintance of mine, useful for the magnum opus. Chap by the name of Mikel Arenaza. Belongs to Batasuna. Or, at least he did.’

‘To Batasuna? Since when did you start making friends with them?’

Herri Batasuna was the political wing of ETA until the party was banned in the late summer of 2002. For an unreconstructed blue-blood like Julian Church to have an ‘acquaintance’ within its ranks seems as unlikely to me as Saul getting a Christmas card from Gerry Adams.

‘I’m a man of mystery,’ Julian says, as if that explains it. He is tapping something on his desk. ‘Truth is, Mikel approached us a few years back with an investment proposal we were obliged to turn down on ethical grounds. Hugely entertaining individual, however, and somebody you should definitely look up. Bon viveur, ladies’ man, speaks immaculate English. You’ll like him.’

Why does Julian think that I would like a ladies’ man? Because of suspicions he has about Sofía? As a consequence of Saul’s interventions over the weekend I am trying to suppress my wilder flights of paranoia, but there is something I don’t like about this. It feels like a set-up.

‘So you stayed friends? You and this Mikel? A representative of a terrorist organization in cahoots with the boss of a British private bank?’

‘Well I wouldn’t say “cahoots”, Alec. Not “cahoots”. Look, if it makes you uneasy, God knows I understand…’

‘No, it doesn’t make me uneasy. I’m just surprised, that’s all.’

‘Well then, fine, why not give him a call? Natalia will email you his details. No sense in spending all of your time up there lunching with lawyers and car salesmen. You might as well enjoy yourself.’