IT seemed too good to be true. Having spent a long day standing freezing on the causeway across the Kyle of Tongue, on Sutherland's north coast, waiting for any intelligence on Naomi Mills and Matthew Brooks, I was driving home.

I could not help but laugh when I saw a couple fitting their description walking down the road about four miles outside Tongue. Surely it couldn't be them.

But it was. They were dressed in dark outdoor clothing, both with black woolly hats pulled down over their heads.

With rucksacks, I think, and he seemed to be carrying something like a net used for landing salmon.

I passed them and looked in the mirror. They appeared completely unperturbed, engrossed in each other as they walked intertwined on the road to Altnaharra.

Not many people walk the 18 miles to Altnaharra, intertwined or otherwise, at 6.30pm in March.

Yes, he was considerably taller than she was, a foot perhaps. So I stopped about half a mile down the road in a lay-by overlooking Loch Craggie, and watched as they made their way towards me.

What to do?

Do I get out and approach them? ("Excuse me, I am from The Herald and I was wondering if...")

What happens if they immediately take to the hills and the man from The Herald has ruined the best lead the police have had all day? Ridicule all round.

Or what happens if it is an entirely innocent couple who think they are being propositioned?

I called the police and they told me to stay where I was. By this point the couple were approaching fast. They would clearly think it strange that a car had stopped in the middle of nowhere, with the light fading fast.

So I pretended I was having an angry conversation on my mobile phone, and they passed unawares. They walked on and round the corner.

Shortly afterwards, the police arrived and took off, speeding past where the couple would have reached. On they went, until out of sight.

I waited a while and there was nothing, so I phoned the police to suggest that, however implausible, they may have just passed them on the road.

Ten minutes later, all but one of the police vehicles returned. They had left the dog van down the road, and were going to work their way back. They suspected the couple were hiding under a bridge.

I was then advised to return to Tongue. About 8.15pm, I was informed that a couple fitting their description had been traced. I think I already knew.

Earlier, Chief Superintendent Ramsay McGhee, heading the inquiry, said that his force was working with West Mercia Police to try to establish a reason for the couple coming to Sutherland.

Mr Brooks was known to have had an affinity for Scotland, but his connection had been to the Loch Lomond area. There was nothing to indicate he had ever been to Tongue before.

However, the searches continued to focus on the area around the Kyle of Tongue where their car was found.