ONE day you might spot him. The first clue will be his motorbike, parked by the roadside. Then your eye will be caught by the rider hacking back at the verge weeds, or perhaps clicking away with his camera and making detailed notes in a pad.

Don't worry. He is not one of those men police warn us not to approach. Instead, Stuart Wilson would welcome your company so he could share with you one of his passions: the milestone.

Mr Wilson has always been interested in history. He has made regular appearances in the letters section of this page, often writing about conservation issues.

His interest in milestones started about two years ago when he decided to take a closer look at the ones he saw regularly on the journey from home in Acomb to work in Sherburn-in-Elmet.

"I saw them every day, gradually disappearing as the grass was growing around them," he said.

"So the first thing I did was go and clear the grass away and make them visible again. That began an interest in looking for more and more of them."

Stuart talked about his new interest at his workplace, Kruuse UK, part of a Danish company which supplies equipment to vets. Soon several of his colleagues were on the lookout for these historic landmarks.

Stuart now studies old Ordnance Survey maps, which mark the location of milestones with the letters MS, or MP for milepost. He then rides out on his motorbike to see whether each stone is still in place. If it is, he tidies away the undergrowth, takes a picture and notes the details.

He has also joined the local branch of the Milestone Society.

"I went to a few of their meetings and realised there were quite a few milestones supporters around the Yorkshire countryside."

The society was launched in 2001. It aims to: promote awareness of the historical significance of milestones; campaign for their retention as part of our national heritage; and research and publish their history.

Milestones date back to Roman times. Those master road builders erected them throughout their vast empire, and 110 survive in Britain.

"Romans measured a mile as a thousand paces of a soldier," Stuart said.

"A lot of Roman milestones have been removed from the side of the road because they are a piece of antiquity.

"If you go behind the Ark in Tadcaster there are three stone milestones embedded in the back yard presumably for safekeeping.

"One of those was originally on the York to London road at the village of Stutton where I used to live. It's old name is Stutton-cum-Hazlewood

"I remember my mother showing it to me when I was five years old."

Like so much else, milestones disappeared from the landscape after the Romans left.

This was bad news for travellers. In remote areas such as the North York Moors, people often perished after becoming lost without features to orient themselves. To stop this happening, William III decreed that guide stones be installed in such regions.

In 1663, the first non-Roman milestones in Britain were put up in Kent. Just over 100 years later, milestones became compulsory on all turnpike roads.

For centuries, milestones were our only street furniture and they were vital information points. Today they are often neglected. They face two main dangers: modern mowers wielded by people who cannot see the stones for the grass; and cars veering of the road onto the verges.

"Ones between York and Malton are particularly at risk," Stuart said. "They are only about 18 inches high and they are just made of cast iron and would break quite easily if hit by a car."

For this reason and others, some milestones have vanished without trace.

"Some of them are protected monuments, like horse troughs. That doesn't always happen. Sometimes these milestones do disappear," Stuart said.

Two have disappeared around York in recent years.

One was at Bilton in Ainsty, between York and Wetherby, the other near Fairfield Manor on the York-Easingwold road.

"Another one has disappeared between Malton and Pickering, a beautiful cast iron one without a stone back."

Yet more have been lost since the war. "In 1940 a lot of milestones were actually removed on government orders in case of an invasion by the Germans.

"They could have dug them up and taken them away, or buried them on the same spot.

"It wasn't that long ago that someone detected one of these buried milestones in West Yorkshire. They dug it up with a JCB and got it reinstated."

Because there have never been any rules governing their size and shape, milestones are different wherever you go.

In contrast to the 18-inch Ryedale waymarkers, Stuart has come across some imposing ones in the West Riding. They are several feet high.

"People have told me it could be for horse riders, who are that much higher off the floor. It could also be for the coach passengers."

Stuart has also found milestones which double as mounting steps for a horse rider. In the North of England, these seem to be peculiar to the East Riding.

"Stone was quite an expensive material to work in. Somebody had the bright idea to give them a dual purpose and turn them into steps.

"If you could use the milestone for mounting a horse, then that's an added benefit."

Once you take an interest in milestones, they lead you down the road to other aspects of local history, he said.

"Driving from Tadcaster towards Ferrybridge, I spotted this milestone.

"I then realised that was part of the Great North Road between London and Edinburgh which at one time came through York."

More research revealed that the milestone, at Brotherton, marked the spot where the Great North Road split into two sections, one running through York, the other through Wetherby. They rejoined into one road near Northallerton.

Over the last two years, Stuart has collected details of no fewer than 500 Yorkshire milestones. "It's a lifetime thing. The Milestone Society wants to log every one in the UK," he said.

So next time you see a biker hacking back at the roadside undergrowth, give him a wave. It'll be Stuart, striving to protect our heritage.

Updated: 11:11 Monday, December 16, 2002