Find Madeleine! The papers were telling us to, broadcasts - including my own - were imploring people to. On my final day in Portugal, I thought perhaps I had. A mix of a journalist's paranoia and incredible wishful thinking.

On Friday, after seven heavy days on the Algarve reporting the story of missing Madeleine, I was coming home. But with two hours to kill before I'd need to start the drive to the airport, I thought I'd go, briefly, to an Atlantic coast beach.

I had a quick surf. Coming out of the water a British man asked me if the water was cold. "Not too bad" I replied noticing, as I did, his partner and two young children: one, a baby, the other a little girl of perhaps three or four. Who - to my untrained eye - looked very like the newspaper pictures of Madeleine.

What to do? This was a happy looking family who just happened to be on an all-but deserted beach an hour or so from Praia da Luz where Madeleine disappeared. I was 99% sure that this girl wasn't Madeleine: she looked happy, as did her well-balanced looking family. But what if it was? What of my 1% niggling doubt?

So I did what anyone would. I prevaricated.

I bought a salad at the cafe overlooking the beach. And looked over the beach, straining my eyes towards the little girl, playing happily in the sand. I got a Portugese newspaper and tried to compare its photo of Madeleine with the girl fifty metres down the beach. I ummed and ahhed. Of all the awful scenarios that may have befallen Madeleine, the most positive is that she had been kidnapped by a couple who had lost their own child - a sort of forced-adoption. In that case, the couple would treat her as their own: a week on the child might not show any obvious sign of distress. With that, I decided. The consequences of not saying anything outweighed the embarassment of doing so. If I said something to the family and was wrong, it would be awkward. If I said nothing and it were Madeleine, I'd miss the chnace to end the anguish of a distraught family, I'd fail to 'save' the little girl . . . and I'd miss the scoop of my career.

I decided my tactics in advance. I'd come clean immediately: I was journalist who'd been covering the McCann story all week so it was - I'd explain - my paranoia asking what I was about to ask. As parents, I'd explain, they'd appreciate my concern. And then I'd come straight to it: was this definitely their daughter? Could I take a closer look? I didn't expect, of course, that the 'parents' of this girl would come 'clean' straight away but I thought there'd be some giveaway in their reaction if this wasn't the happy scene it seemed. And, close up, I'd be able to look into the little girl's eyes: the Portugese papers had pointed to a slight birthmark within Madeleine's eye.

"I can assure you she's our daughter", the man said, understandably put out. "She has been and continues to be." He seemed genuinely cross, and in a 'how dare you' kind of way rather than a 'you've rumbled us' way. "I'm sure she is" I replied. And, geniunely, I was. But now that I'd embarassed myself so much, a little extra dose wouldn't hurt. So you wouldn't mind me just having a quick look in her eye? Now I was the weirdo.

He didn't really get a chance to reply. I just had a look: no mark in the eye, not Madeleine. A few metres off, the girl's mother smiled in a 'it's OK, I understand, you weirdo' kind of way. The man just glowered.

I slunk off. "Very embarassing", I muttered, "so sorry to have disturbed you." Deep down though I was pleased I'd approached them. Imagine I'd said nothing, and had to sit on the plane home, the 1% doubt growing with every passing mile.