João interrupts again. If only Six had ears on Carmen’s landline.

‘I’ve been so stupid,’ she continues. ‘I tried to pretend that this was not going on, but there have been so many things, too many coincidences with Arenaza and Juan Egileor. I don’t know what to do about it.’

I step away from the sink, flush the loo and go back into the kitchen. Hearing Mikel’s name brings a pump of blood to my head. What does she mean about coincidences involving Arenaza and Egileor? That she suspects Maldonado and de Francisco of conspiracy in their disappearance? Carmen now responds to something João has said:

‘I can’t resign. What will I do? I’ve seen the emails with Chakor’s name on them. You’ve seen the bank statements. We’re talking about three-quarters of a million euros of public money, maybe more. God, maybe I shouldn’t even be speaking on this phone. What happens when this man wakes up and starts saying that he was ordered to kill Orbé?’

Again João interrupts and Carmen’s subsequent response – ‘Of course that’s what happened’ – would indicate that he questioned whether or not Mohammed Chakor was paid by elements in the Interior Ministry to assassinate Tomás Orbé.

‘What if they trace it back…’ But Carmen is unable to complete the thought. ‘What if… I don’t even want to think about that. I can’t believe that this is happening.’

I have heard more than enough. On the evidence of this telephone call alone, Kitson must alert London and set in motion the SIS plan to disgrace de Francisco and Maldonado. How they do that, at this late stage, without the dirty war becoming public knowledge, I have no idea. But my work with Carmen is done. I now need to get out of her apartment as quickly as possible, to call an emergency meeting with Kitson, and to assist him as best I can. The last thing I hear her say, in Spanish, is, ‘I am a patriot, you know that. I believed in him. And now I feel so stupid. But I don’t want to betray my friend,’ as I switch on the extractor fan above the stove, grating cheese onto a plate. Sixty seconds later Carmen goes into the bathroom, locks the door and does not emerge for another ten minutes. I knock once, asking if she is all right, but she responds only to tell me to boil a pan of water for the pasta. When she comes out, I put my arm round her shoulder and she shrugs me off.

‘What was that about?’

‘What was what about?’

‘The phone call. The argument you were having. Are you OK?’

‘It wasn’t an argument.’

‘It sounded like one from where I was standing.’

She takes a corkscrew out of the drawer beside the stove and stabs it into the neck of the bottle of wine.

‘And where were you standing?’

‘In here. You sounded very upset.’

‘It’s just a problem at the ministry, OK?’ The cork pops. ‘Can we not talk about it?’

The escalating tension here might work in my favour. If I can manufacture a full-scale argument it may give me an opportunity to leave and to contact Kitson within the next thirty minutes.

‘But I’d like to talk about it,’ I tell her, trying to sound patient and concerned.

‘Well I would not,’ she spits. ‘Can you just stir the sauce, please?’

And here is my opportunity.

‘Don’t talk to me like that.’

‘What?’

‘I said don’t order me around. You said you were going to cook dinner for me tonight, so you stir the fucking sauce.’

It is our first row. A sullen, intolerant sneer makes its way across Carmen’s face as she leaves the room. She looks like a spoiled child.

‘Oh don’t just storm out.’

Under her breath she insults me, quite effectively – Cerdo! – and slams the bedroom door. I am so wired by the prospect of seeing Kitson that I experience only a momentary beat of sympathy for her wretched predicament. This lasts about as long as it takes me to collect my coat from the hall. Then I leave the apartment, slamming the door with my own brand of adolescent petulance, and hurry down the stairs to the metro.

40. Line 5

‘This, as they say, had better be worth it.’

I have pulled Kitson out of dinner at the Taj Mahal with Ellie, Michelle and Macduff. He still looks exhausted, but his mood appears to have lightened considerably since Starbucks.

‘Was just about to have my first mouthful of chicken jalfrezi when you called,’ he says. ‘Bottle of Cobra on its way, sag aloo, a nice peshwari nan. First normal food in weeks. Not bloody jamón, not bloody tortilla, not bloody chorizo. I’ve been running on a single poppadum since lunch, so make it snappy.’

We have met in the ticket hall of the metro station at Callao. He clunks through the metal barriers and we head down the stairs to the southbound platform of Line 5.

‘You wanted information out of Carmen,’ I tell him. ‘I’ve got it.’

‘Already?’

‘Believe me, you won’t be going back to finish your curry.’

We find a bench at the far end of the platform and sit down beside one another, about ten metres from the closest passenger. Kitson is wearing hiking boots, a checked shirt with a frayed collar, a bottle-green V-neck pullover and a badly patched tweed jacket. He looks like a sheep farmer who took a wrong turn at Dover. I tell him everything that I can recall from Carmen’s phone conversation – that she suspects Maldonado and de Francisco of diverting public funds to bankroll a secret state operation against ETA – and he nods along, alerting me to the fact that he has triggered the digital voice recorder in the outer pocket of his jacket.

‘This is dynamite,’ he keeps saying, ‘fantastic stuff,’ and I experience the exquisite high of a colleague’s recognition and praise. ‘João’s details were in the address book you lifted from Carmen’s mobile. If it’s the same guy, he’s an old friend of hers from university who works at the Banco de Andalucía. She must have asked him to look into the money trail.’

‘Makes sense.’

‘And she said there was three-quarters of a million euros?’ He lowers his voice slightly here. ‘Did she quote that exact figure?’

‘That exact figure. Why?’

Kitson removes the jacket and places it across his lap. It’s stuffy down on the platform and the air is hot with pollutants. ‘We have a separate confirmation of a slush fund controlled by de Francisco with around 765,000 euros in it, traceable to several Interior Ministry bank accounts.’

‘It’s not a great deal of money.’

‘No.’ We have both arrived at the same conclusion. A figure that small would suggest that we’re either at the edge of a much bigger problem involving far larger sums of money or, more likely, that we’re only dealing with a dozen or so individuals running a highly secret operation against ETA under the operational and financial control of Félix Maldonado.’

‘That’s what your diligence is throwing up?’

He nods. At the top you have Maldonado and de Francisco directing orders and covert funds, most of it diverted from government coffers, to three key individuals: Luis Buscon, Andy Moura and Sergio Vázquez.’

‘Why haven’t you mentioned those names before?’

Kitson looks at me, those calming, unchallengeable eyes. ‘Don’t take it personally, Alec. Plenty of people were out of the loop on this one. That’s just the way I like to run things. Believe me, after the work you’ve done on this, London are going to be cock-a-hoop. SIS have stepped into the breach and saved the day. The Spaniards have a problem in their own back yard and it took the Brits to solve it.’

I don’t respond to this and, in fact, my elation is no sharper than it was moments ago.

‘Who’s Andy Moura?’

‘High-ranking Guardia Civil in Bilbao with a lifelong contempt for all things Basque. On record as saying that ETA could be destroyed within five years if only the police were allowed to do “whatever they want”. Basque pressure groups have been after him for years. Cast-iron thug. Has survived three attempts on his life, two car bombs and a shooting.’