hank God. It's Saturday morning and I've managed to avoid Ed since Thursday night. Okay, I know it's only one day, but I told Jo to tell him I was in a meeting when he called, and then yesterday, at around three o'clock when I knew he'd be at work, I rang his answer machine at home and told him I missed him and that I was fine, but really busy, and I'd have to work on Saturday but I'd call him in the evening, and maybe we could get together on Sunday.

Not that I am missing him. That's what's so extraordinary. I've loved having two nights in at home by myself. I haven't picked up the phone once, I've just pottered around, watching TV, reading magazines. I even attempted a bit of DIY and hung some pictures that have been propped up on top of the radiator since I moved in.

I thought that these 'days off, as Jules put them, would be a time of reflection. I thought I'd be sitting around analysing every aspect of our relationship and trying to work out whether Ed is The One, whether I do want to spend the rest of my life with him, but actually I haven't even thought about him. I've been far too busy being happy by myself.

Which I suppose is slightly worrying in itself.

So when the phone rings on Saturday morning, again I leave it because I've assumed it's Ed, but of course I leave the volume up just in case it's someone important like, well, I suppose like Jules, because really she's the only person I feel like talking to at the moment, not to mention the only person who really needs me right now.

Jamie moved back in two days ago. Jules was trying to be cold, trying to let him know that they couldn't simply pick up where they left off, but, as she admitted to me in a whisper while Jamie was downstairs, 'God, Libby, it's so nice to have him home,' and her coldness towards him is warming up by the minute. Make that the second.

And I know, she knows, it won't be forgotten about, and the strangest thing of all is that, hearing this, I started kind of rethinking the whole marriage thing. Not that I don't want to get married, it's just that maybe it isn't the happy ending. Maybe the marriage is just the beginning. Maybe getting married isn't going to be the answer to my prayers after all.

I mean, Jesus, it wasn't exactly the answer to Jules's prayers now, was it?

It isn't Jules. It's Nick.

I trip over the rug and stub my toe on the coffee table as I'm rushing to the phone to pick it up before Nick rings off and I pick up the phone shouting, 'Shit!'

'Is that any way to greet your second-favourite man? If I piss you off that much why bother picking up the phone at all?'

'Ouch,' I say, rubbing my toe. 'I just stubbed my toe.'

'Have you looked out the window?'

'No. Why? Are you sitting on my railings?'

He chuckles. 'Nope. But it's a beautiful day. Far too nice to be staying inside. What are you doing?'

Like I even have to think about it. 'Nothing. Absolutely nothing.'

'Not spending the day with your fiancé, then?'

'Nope. He thinks I'm spending the day in the office.'

'Oops. Do I smell trouble on the West London front?'

'Nah, not really. I just needed a bit of space. Anyway, why are you asking?'

'Just wondered if you wanted to come out to play.'

'What kind of play?'

'Not that kind of play,' he laughs. 'Although now you mention it—'

'What do you want to do?' I resist all temptation to flirt.

'I thought maybe we could go for a walk on the heath, then window shop in Hampstead, maybe have lunch or something.'

'That sounds fantastic!' It does. 'I'd love to.' I would.

'Great! How about I'll meet you outside the cinema on South End Green.'

'Okay. Give me an hour.' I look at my watch. 'I'll see you at twelve.'

'See you then.'

And for the first time in what feels like ages I don't have to worry about what to wear. I don't have to worry about 'looking the part', or being accepted, or wearing designer gear. I sling on my jeans that haven't seen the light of day since I met Ed, pull on some trainers and inch on a tight, white, V-necked T-shirt. If I were with Ed, I'd loop a cardigan stylishly around my shoulders, but, seeing as it's Nick, I tie it round my waist and to be honest it's far more comfortable that way, at least I don't have to worry about it falling off.

I slap on a bit of make-up — because even though this isn't a romantic assignation, I wouldn't be caught dead leaving the house without something on — toss my hair around a bit and that's it. I'm ready.

And when I reach the cinema at noon, Nick's already there, sitting on the steps outside reading the Guardian, occasionally looking up and closing his eyes as the sun bathes his face in warmth.

There's a girl leaning against a lamp-post trying to look as if she's also basking in sunlight, but as I approach I watch her sneaking looks at Nick, who is looking, it has to be said, decidedly gorgeous.

'Libby!' He stands up and flings his arms around me, giving me a smacker on the cheek, and as we walk off down the road he keeps an arm casually around my shoulders, and maybe this should make me feel uncomfortable, but there's nothing sexual, nothing intimate, it's just the mark of a good friend, and I laugh as I put my arm around his waist and give him a squeeze, instantly remembering the hard contours of his body, the way he looks when he is naked.

But then I remember I am the property of another, and I move away from him slightly, just enough for him to remove his arm, and I link arms with him instead, which feels much safer.

'Come on, come on,' he urges, marching next to me. 'If I'd known you were such a snail I wouldn't have asked you to come for a walk.'

'We can't go for a walk yet,' I say in horror. 'It's practically lunchtime and I haven't had any breakfast. I'm starving.'

'Okay. Shall we hit the high street?'

'To the high street we shall go,' and giggling together we march up Downshire Hill.

'God, this is beautiful,' I say halfway up the hill, stopping to peer into the windows of a tiny, cottagey whitewashed house.

'Mmm,' agrees Nick. 'This is one of my favourite roads in the whole of London. If I had money I'd definitely buy a house here.'

'Money?' I look at him with horror. 'But Nick! You're forgetting. You don't want money. In fact, if I remember correctly, you'd give it all to the bloody politicians.'

'Ah,' he says, nodding sagely. 'Yes, that is correct. I did once say I would give my lottery win to the bloody politicians, but of course I'd save a few million for myself.'

'You've changed your tune.'

'Yes, well. As you keep saying, I'm really a girl, and isn't it a woman's prerogative to change her mind?'

I laugh. 'Are you quite sure you're not gay?'

'Never!' he exclaims loudly in a Winston Churchill voice. 'When there are so many gorgeous women around.' He leers at me and tries to pinch my bum as I shriek with laughter and run off.

'Wait, wait,' he calls, and I stop and grin at him as he lopes towards me. 'I am sorry m'lady for insulting you by partaking of your bottom.'

'You're forgiven,' I say, 'just don't make a habit of it.' And then I get this flashback of Nick kissing my breasts, down to my stomach, and I shiver, horrified that I'm still thinking about it, that the memory of it, in the presence of the man himself, is definitely turning me on. I shake my head to try and dislodge the memory, but of course Nick is here, with me, so it doesn't really go away, just moves to the back of my mind, which seems to be fairly safe for now.

We walk past the police station, past a cafe, and as we pass the furniture shop on the corner I stop Nick and drag him to the window.

'It's gorgeous,' I sigh. 'Can we have a look?'

'Yes. Let's go in and look at all the things we could never afford.' And then his face falls. 'I mean, me. Sorry. I keep forgetting that you can probably afford the whole shop. A thousand times over.'

'Not yet, I can't. Come on.' I drag him in by the hand. 'Let's drool.'

I sigh with delight over the ethnic furniture, and shriek with horror at the prices.

'They want £970 for that piece of Indian tat?' says Nick very loudly, as he looks at the price of a coffee table.

'Sssh. Keep your voice down,' I whisper, noting that the sales assistants' eyes are following us around the shop. Just as we walk out, Nick says, loud enough for the entire shop to hear, 'You know Simon bought the very same table in India for £3.20. And what's more, he thought he was ripped off.'

'You are incorrigible,' I laugh, as we step outside.

'But really,' he insists. 'Those prices are laughable. And they do probably buy it in India for nothing. Think of all those poor people struggling in India, and thinking they're getting a bargain by selling their handcrafted stuff for a fiver.'

'Hmm.' I can see he has a point. 'Are you getting on your political high horse again? I just want to be warned.'

'Nah,' he says, 'the weather's far too lovely to get on any horse. Much more fun walking.'

We continue up the hill, idly chatting about this and that, and then I remember how mysterious he was the other night about the book, and what's happening with it, and I ask him again if he'll tell me.

'Can't.' He shakes his head. 'It's a secret.'

'Oh, pleeeeeeeeeeaaaaaaase,' I plead, looking up at him hopefully. 'I'll be your best friend.'

'Nope.'

'What about if we exchange secrets?'

Now he looks interested. 'You mean you tell me one, then I'll tell you?'

He stops walking and turns to look at me. Now he's interested. 'Okay, I'll do a deal with you. You tell me a secret, and if I think it's good enough I'll tell you. How's that?'

'Okay, deal.' And I stand there desperately trying to think of a secret, but I can't think of any. I could tell him that I cried during sex the other night, but I don't want him to know that, it wouldn't be fair on Ed, and anyway it isn't really a secret. But I don't really have secrets. And then I think of something.

'I've got one, but you have to promise you'll never tell anyone.'

'I promise.'

'It's really stupid.'

'Libby! Just tell me.'

' Okay. When I'm driving in my car I talk to myself.'

'So? Loads of people talk to themselves.'

'But I do it in an American accent.'

'You're kidding!'

I shake my head.

'Give me an example.'

I shake my head again.

'Oh, go on, just give me an idea of what you say, what you talk about.'

Reluctantly, it has to be said, I stand in the middle of Hampstead High Street and in a crap American accent I say, 'Did you have a good time tonight? Yeah, it was rilly cool.'

And Nick collapses with laughter.

'I can't believe that,' he splutters, and I start laughing too. 'You are seriously weird.'

'I am not. I bet loads of people do that.'

'Not in an American accent. Go on, do some more.' He wipes the tears from his eyes.

So I do a little bit more, and soon the pair of us are clutching each other to stop from falling down, and I'm holding my stomach because I'm laughing so hard it's hurting.

And when we recover I say, 'Your turn. Now tell me about the book.'

'No way. Your secret wasn't big enough.'

'What? You're joking! You loved my secret.'

'Only because it demonstrates what a completely weird person you are. It isn't that big a secret.'

'You bastard.' I hit him.

'Wanna try again?'

'Nope. You're not getting any more secrets out of me. Now I really am starving, what about here?' We're standing outside a cafe with tables dotted on the pavement, and I watch a couple leave a tip, then stand up.

'Quick, quick.' Nick grabs me by the hand. 'We must have that table.'

I order a salade niçoise, and Nick has an egg and bacon baguette, but by the end of the meal we're feeding each other our respective meals, making a huge mess, and giggling like children.

And Nick insists on paying, which I feel slightly guilty about, because he really doesn't have much money, but he won't hear of accepting anything from me, and then we leave and walk up, past Whitestone Pond, and on to the heath.

And the weather is beautiful. It's a hot, hazy, lazy summer's day, and everyone's smiling, and this is London at its best, it's why I wouldn't live anywhere else.

After a while, kicking through the long grass until we're on open spaces, Nick says why don't we sit down and sunbathe for a bit, and I put my bag down, kick off my shoes and fold my arms behind my head, just listening to the birds and watching the trees blow slowly in the soft, occasional breeze.

'So,' I say eventually, when we've been lying there for a bit in silence. 'What did you think of Ed?' I don't know why I ask this question, but I suppose I think he'll echo Sal and say he seemed like a nice guy. I'm certainly not expecting what comes next. If I had been, I would never have asked.

'Do you want the truth?' Nick says seriously, and I shrug.

'I think he's awful,' Nick says slowly, while I look at him with a smile because he's obviously joking.

He's not joking.

'I think he is absolutely horrific,' he says, and there isn't even the merest hint of a smile. 'Not only is he far too old for you, he's also far too straight for you. He's pompous, arrogant, and he doesn't fit into any aspect of your life. He treats you like some sort of trophy girlfriend, sorry, fiancée, with patronizing comments and pats on the head, and he has completely ignored who you really are because he's just not interested. He probably cannot believe his luck that someone like you would even look at him.

'And to be honest,' he continues, while I sit open-mouthed in shock. 'I can't believe you would even look at him. I think he is quite possibly one of the most awful men I have ever met, and all I can think is that you've had some sort of mental block, because you would have to be absolutely crazy to even look at him, let alone consider marrying him.'

I'm about to scream at him, to shout 'How dare you,' to splutter with indignation, and fury, and rage, but I don't. Nick just looks at me, waiting for a reaction, and I feel my eyes well up, and suddenly I'm crying. Hiccuping huge sobs, and before I know it Nick has his arms around me, and he's rubbing my back in great big circular motions, and I'm soaking his shoulder with my tears.

'Sssh, sssh,' he's saying. 'It's okay. It's all going to be okay.' And this makes me cry even more, because, even though I don't want to be influenced by what Nick has just said, I know he's right. He's absolutely fucking right.

And eventually I calm down, and pull away and try to smile through my tears, finally absolutely sure that I have to end this with Ed, that I cannot go through with it, and Nick smiles at my wobbly smile, and Christ only knows how this happens, but we're kissing.

It's not that I kiss Nick, or that he kisses me, it just happens. One minute I'm smiling at him and the next second I'm locked into his arms.

His lips are on mine, and they're soft, and warm, and then, before I even register what's happening, my tongue takes on a life of its own and slips into his mouth, and he pushes me back on the grass and a moan escapes me, from somewhere deep down, and I want his kiss to swallow me up.

We can't stop. Neither of us. Not even when a group of teenagers walks past and starts catcalling and shouting things. I am lost in this kiss, in Nick, and I want it to go on for ever.

Does it sound clichéd to say that everything disappears? That it's as if there is nothing else on this planet except me, and Nick, and the feelings that are churning up inside me, feelings that I had honestly forgotten I ever had? That if we had not been in a public place there is no question that we would have ended up having sex? That when Nick's hand disappeared up my T-shirt to gently rub my breasts I would have let him carry on for ever had it not been for my sense of decorum?

But we have to stop. Eventually. And as we pull apart and look at one another, my hands fly up to my mouth. 'Oh my God,' I whisper. 'What have I done.'

I am not the sort of person who is unfaithful, and, before you argue with me, I consider kissing someone, when you are engaged, going out with, or married to someone else, unfaithful.

Many years ago I caught Matthew, an old boyfriend, with someone else. When I say caught, I don't mean that I walked in on them, interrupting coitus, as it were. I mean that I was in the wrong place at the wrong time (or perhaps you would argue the right place at the right time), and that Matthew had no idea I would be there, and that I saw him kissing someone else.

It was a crowded party, and yes, admittedly, I was far too young to be getting serious with anyone, let alone Matthew. I stood there and watched them, frozen with horror, and I thought that my heart was actually going to break. Many years ago Matthew argued that it was only a kiss, that she was no one, that they hadn't even petted, let alone slept together, so what was the big deal about. But I vowed, there and then, that I would never do that. I decided that if ever I were in a relationship that made me so unhappy I was looking for emotional or physical gratification outside that relationship, I would first discuss it with my partner, and together we would try and work it out.

Of course I now know, thanks to Jamie, that nothing is quite as easy as that. I have surprised myself with the way I seem to have forgiven Jamie committing what I have always considered to be the cardinal sin, but there again, as Jamie confessed, it was simply physical gratification, which, although I don't condone, I can sort of understand.

But the thing that's worrying me now, the thing that I could never have predicted, is what on earth you are supposed to do when your feelings are unfaithful?