From a safe distance at the edge of the gathering of birthday well-wishers on the Grid, I watch Harry covertly to see if he is aware of, or interested in, the way Ruth glances at him as she makes her announcement, and am startled to see a slow flush of colour suffusing his face as he avoids looking at her directly. His face is carefully neutral in expression, but the flicking of his fingers against his left leg suggests that he is keen to escape her gaze, and as he turns away to engage Tom in conversation, I sense rather than see his relief.

Perhaps he finds it embarrassing, I think, as I sit quietly, nursing my drink. After all, there would have to be an age gap of fifteen years or more for one thing (but that's not really too bad, or so I would like to think), and for another, it's the oldest and most tired cliché in the book – a naïve young woman falls in love with her older and more worldly boss - and then there's the fact that Ruth is nothing, nothing, like any of his other women. Where they are overtly sexual, she is modest and shy to the point of painfulness. Harry has always gone for confident, aggressive, hard-edged women, women who demand what they want and know how to get it, women who don't take things too seriously. But I know that a relationship with Ruth would be a delicate and slow undertaking. To move too fast, would be to lose her forever. I know that Ruth isn't sure of herself, doesn't know her own worth, can't quite conceive that someone might think her absolutely marvellous just as she is. I know all these things, because they are true for me, too. Ruth and I are so similar in that regard, you see. We are so alike, even down to our admiration for the same man.

A couple of hours later, I find myself offering to drive Ruth home, as she has had more celebratory champagne than perhaps was wise, and I have had just the one glass of Beaujolais, at the start of the night. Everyone else has left, the younger ones – Danny, Zoe, Sam and even Colin, going on together to a riverside nightclub, while Tom left not long after the CIA liaison, Miss Dale, took her leave, an hour or so earlier. Harry is ensconced again in his office, door shut, blinds closed. That could mean anything, I think, as I see Ruth standing at her workstation, looking uncertainly at the Inner Sanctum, as the Section refers to Harry's office, although never in his hearing. I cough slightly as I approach her, so as not to startle her in the gloom of a half-lit and almost deserted Grid, and she turns towards me with a small smile which does not quite reach her eyes. "He's not actually going to work now, is he?" she asks me. "I mean, surely not, not on his birthday!"

I gently tell her that Harry hasn't actually cared about his birthday for as long as I have known him, and she looks stricken at the thought. I ask her if she would like a lift home rather than risking the bus at this time of night, and to my surprise, she accepts gratefully. She's not really drunk, just what my mother would call tipsy, but bravely, I offer her my arm as we leave the Grid, and she takes it, saying that so few men nowadays ever think of the little courtesies that make life civilised. Yes, I'm definitely a dinosaur to her. As we reach the pods, we have to separate to walk through them, and I suddenly become aware that I'm being watched, with that sixth sense that all spooks develop if they live long enough. I turn round to see Harry standing at the doorway to his office, and while I can't see his face in the semi-darkness of the Grid, I can feel the strange intensity with which he is watching us, and a shiver runs up my spine.

Once through the pods, Ruth slips her hand back under my arm as we walk together to the car park lifts in the foyer, and Harry's stare seems to take on a laser-like quality. I hurry her along, into the lift, down several levels, and then into my car – an old silver Rover I inherited from my father – before Harry decides to follow us out. Ruth settles herself comfortably into the worn red leather of the passenger seat, and runs her hand lightly over the burl walnut coachwork of the dash. "It's beautiful, Malcolm, a really fine old motor. They don't make them this way any more, do they? It's a bit like yourself, really…do you know how rare it is to meet a true gentleman these days?" She turns in her seat to look at me, and I have to remind myself to concentrate on driving safely out of the garage, instead of looking into those eyes, glowing softly now. Her eyes are always the best indicator of her mood, I have observed, but I have never seen them looking like this. Not at me. It's the champagne, I decide, giving her a half smile in reply as I swing the car out onto Horseferry Road.

I know where Ruth lives – we all know where each other lives – so she settles back and watches London slip past the window, while I take the long way to her house. If she notices, she doesn't say anything. That's a good sign, I tell myself, trying to calm my racing heart by doing impossibly long divisions in my head, reciting the periodic table (backwards as well as forwards) and constantly reminding myself to focus on the road, and not on her. My hands tremble on the wheel, as I have to talk myself through each gear change. It's ridiculous, for a man who has been driving for almost longer than she's been alive. The traffic is light this late at night, and even taking the long way is quicker than I had hoped. As I pull up at her semi-detached Victorian house near Kennington, she sits up and thanks me for driving her home, and I'm just about to say it's nothing, really, it was on my way (which isn't strictly true) when she delicately slides her right hand over my left, which is still clutching the walnut steering wheel, and says my name in that low, soft voice of hers. "Malcolm," she says, and stops. Her eyes go to our joined hands with a puzzled look and then gently, she prises my hand away from the wheel and takes it in both of hers. "Are you cold? Why are you trembling?" I can't get the breath to form a single syllable, and my heart appears to have dislodged itself from my rib cage and relocated to my throat, so I just look at her head bent over my hand. Oh God, let me say the right thing, and grant me the breath to say it with, I pray, while trying to recall if I have an inhaler in the glovebox...damn this wretched asthma!

After what seems like aeons, I manage to gasp out her name – "Ruth!"and she looks up at me. Her eyes are gentle and full of trust, and suddenly the fear leaves me, my chest unclenches, and I can draw breath easily again. I reclaim my hand from hers and with the lightest touch I can manage, I say, "I just wanted to say how very glad I am that you came to Five, and that you'll be staying with us. And that…that…that we're friends. I haven't many real friends, but I'm proud to count you as one." I stop to take another deep, calming breath. Damn it, I sound like a callow youth. Harry would never stutter or shake if he spoke to Ruth, I'm certain. He's too experienced, too cocksure, to be rendered speechless by any woman. Ruth's eyes haven't moved from my face. She has not one scrap of guile, I realise, as I look at her. All her thoughts are in her eyes. I see so many things there – affection, kindness, and that almost ethereal quality which is the most Ruth thing of all. She looks away for a moment, and then speaks, her voice mellow and relaxed with champagne and happiness.

"I'm so pleased that I came to Five too, and that I have made good friends here, but especially you, Malcolm – you were so nice to me when I was making a cock-up of everything in the first few weeks and didn't know one end of the Grid from the other. I feel that I can always rely on you, that you'll look out for me. I meant what I said earlier on, about how rare it is to meet a true gentleman. You're a wonderful person. Thank you for bringing me home." And then she reaches over to kiss me on the cheek, a butterfly's kiss, the merest brushing of her soft lips against my skin, and in the next moment she has slipped out of the car with a little wave goodbye and says softly, "Good night, and sleep well – see you on Monday!" before entering her house. She crouches to scoop up the cat that has come to greet her as she opens her front door. Resting her head against the animal's sleek fur as the cat drapes itself over her shoulder, its paws kneading her shoulder with feline delight at her return, she goes inside.

I sit in the car outside her house for a few minutes more, reliving the moment of that gossamer kiss, and hearing the kindness in her voice as she told me that we were friends, nothing more, but also nothing less. The car is scented with her light perfume, which reminds me of a garden after rain. I touch the still-warm headrest of the passenger seat, as if to confirm that she was there at all. Then I touch my cheek, where her lips rested for less than a heartbeat, and then I start up the motor, flick on the headlamps, and move off, smiling all the way home. It's a start, I tell myself. And she thinks I'm wonderful! Each time I recall her words, some of the long-held pain inflicted by Sarah dissipates, and in its place is the memory of Ruth's eyes and her beautiful smile. Malcolm 1, Harry nil.