The sun had started to lighten the horizon as I drove home, four hours later. My back and shoulders ached from the finicky work of replicating the damaged files, and there was a thumping headache starting up behind my eyes. Too much to do, too late, too often, I thought as I crept into the house so as not to wake my mother (she sleeps like the proverbial log, but still, it wouldn't do to startle her after her heart operation) and up the stairs to my bedroom.

I envy Harry Pearce his ability to down a couple of stiff whiskeys, then fall asleep anytime, anywhere, but it doesn't work for me. I prefer to stand under the hottest shower I can bear until my muscles and mind are relaxed enough for sleep, washing out the tension of the day. It was nearly four-thirty when I finally fell into bed, and I knew I would have to be back on the Grid in another four hours, but I couldn't sleep. Normally, the hot shower does the trick, but tonight (this morning?) all it seemed to do was wake me up. Or perhaps it was because I couldn't stop thinking about Ruth. Her unconscious grace as she moved, her small, square hands feeding papers into the copier and handing them to me, the way she tilted her head and smiled gently at me as we talked. Her feet, peeping through her sheer black stockings, were finely made. The true mark of a lady, my sainted grandmother would have said. And then there's the rest of her…

I had only ever known one woman in the Biblical sense, and then only a few times, before Sarah left me for some loud, brash City type in an Italian suit – for someone who was everything I'm not. Since then, I had tried my very best to not think about women in that way, especially as Sarah had made it clear that in bed, I was dismal at best and a complete failure at worst. So I threw myself into my work and took long walks on the Heath and went swimming in the Ponds (yes, even in winter) and did everything I could think of to quell those sorts of thoughts and finally, over a period of twenty years, thought I had got myself under control. Even the sights and sounds of our more…intimate surveillance operations didn't get under my skin anymore. I truly loathe the voyeuristic aspect of our work, but I recognise the operational necessity of it. One has to be as detached as a surgeon and as ascetic as a Trappist monk, but it is possible to desensitise oneself to almost anything. Almost.

Now, I found myself struggling to regain that supreme sense of detachment which had served me so well for so long, but failing parlously. Ruth dressed modestly, in long skirts and demure blouses – if you didn't know what she was, you might glance at her and think she was a University tutor, or a holistic healthcare provider - something artsy or alternative. It was a refreshing change from the way most of the other Five women dressed, in tight, aggressively man-tailored clothes that I find intimidating rather than attractive. With Ruth, it's all about understatement. Her clothes skim her elegant curves, hang in soft folds, have frills and tucks and pleats. She looks like she would be soft to touch, not taut and tough. Her hair is a deep chocolate brown, and the way the ends turn under and frame her oval face looks natural. She is the most beautiful woman I have ever met, and I can't get her out of my mind. I wonder what she sees when she looks at me in that kind way of hers. Probably she thinks I'm some old relic in a tweed jacket, too stuffy, a bit timid, spending his days in geekdom, hiding in the back rooms of the Grid because he doesn't have the social skills to cut it in the real world. I finally fall asleep, though, contemplating how it would feel to have her here beside me, her dark hair spread across the pillow, the sheet slipping off her slim shoulder as she turns towards me and…well, it doesn't do to do dwell on what one can't have, does it?

For the next few weeks, I live off the memory of the Customs Tea Party. Oh, I saw her every day of course, and sometimes she would stop for a few minutes' chat if she had the time, but Ruth was being kept busy by everyone else, and as her secondment end date approached, she worked even harder than usual to try and convince Harry to keep her at Five. Indeed, her zeal was noted and remarked on by many on the Grid. I was despondent at the idea that she might return back to Cheltenham, when at the end of a long op involving…actually, that doesn't matter, we'll just say that tonight, Ruth announced that Harry had extended her secondment. Tonight is Harry's birthday drinks, as it happens, and oh, how her eyes sparkled and shone with joy unconfined as she told us. The way she looks at Harry, shyly, from beneath her lashes, is almost unbearable to see, even while I admit to myself that of course, it would have to be him. It would have to be Harry bloody Pearce.

Harry and I go back a hell of a long way, more than fifteen years, in fact. He's my boss, but he's also my friend. Ours is a friendship forged in the heat of battle – I've gotten him out of many a tight spot thanks to my vigilance in the surveillance van, and he has saved my life on more than one occasion. He won my undying gratitude by backing up my story with my mother when he met her at the Security Services ball, early in my career – I hadn't wanted to disappoint her by admitting that I was considered too timid for real spy work, and had instead told her that I was a daring field officer, a true James Bond type – and Harry, straight-faced, had backed me to the hilt, to my mother's great delight. I'd lay down my life for him, and he would lay down his for me. For all that Harry says that there are no friends in our line of work, just colleagues who we die for, he's wrong, and we have the history to prove it.

Harry actually gives a damn about his team; beyond that, he's immensely likeable, and a true study in contradictions. He's well read, fond of Shakespeare, as am I, a hard hearted realist who loves the English Romantic poets, a military man who now negotiates the minefield of politics and the notorious corridors of power in Whitehall with the same instinctive approach that kept him alive as a field agent on the other side of the Iron Curtain. In our world of shifting shadows and allegiances that can be made or broken in a moment, Harry Pearce is that rarest of things, a man so anchored by his own integrity and his personal code of honour, that he has become the still point at the centre of all things Section D, as Connie once observed - perhaps it was the truest thing she ever said. But that's a tale for another time.

To turn to the other side of his character, the side that particularly concerns me now, I can confidently say that when we first met all those years ago, Harry was by reputation the biggest Casanova in the Service, with a string of affairs to his name, plus one bitter divorce and two alienated children. He was ruggedly handsome, blond, charming, and morally flexible, to put it delicately, when it came to sleeping with whomever his eye fell upon.

Now, he's more rugged than handsome and his fair, slightly curly hair has receded (then again, whose hasn't?) but his charm is unimpaired and God only knows what his moral standards, or lack of, are like, after all this time doing whatever he likes, in the bedroom department. Harry Pearce is a force of nature where women are concerned. They sink themselves adoringly in his shadow, they appear to live only to see him again, and when he's around, all bets are off for the rest of us. Sometimes it feels, when he walks into a room, as if his presence fills it to the extent where it becomes difficult to draw breath, especially if he's in a passion about something. Women seem to notice him almost before he enters the room, just as they inevitably fail to see me even when I'm standing in front of them. I have seen it too often to think it mere coincidence. Harry has It, in spades, and I don't even know what It is, where the fairer sex is concerned. If he wasn't such a thoroughly decent sort, who has sacrificed so much in the line of duty, he'd be very easy to hate.

It's his personality, I think, which attracts them most. He's a born leader, forceful and decisive, yet still able to hear and act on the advice of others. He's a formidable opponent, a battle-scarred survivor of more intrigue and Cold War spy work than the rest of his team put together. There's a quirky, mischievous side to him too, which he only rarely indulges in. But most of all, it's his enormous self-confidence and unshakeable belief in what he does, that draws people to him. In short, he is remarkable, and I know how fortunate the country is to have a man like Harry Pearce on constant terror watch. Harry, although he would groan to hear me say it, is the living embodiment of the Service motto, Regnum Defende. Earlier today, as I yet again witnessed Ruth's adoring gaze across the Grid at Harry's office (she would be so mortified if she realised that everyone on the Grid knows how often she does that), another bit of Latin occurred to me, and I adapted it to fit the circumstance: Caveat Ruth. Ruth, beware.