Sat nav units in cars could be considered old-fashioned now. Millions of people have sat nav on their phones or even on their watches.

Paper maps are practically prehistoric. Maps on screens can be enlarged to view a place in minute detail.

So why are Fiona Robson and Terry Moore fascinated by a lump of stone which bears the words ‘To Newcastle 55 miles’ and ‘To Carlisle 1 mile’?

Their interest is less about miles and more about years: 261 of them.

That’s how long the stone has been there, guiding travellers since 1758.

Fiona and Terry are members of the Milestone Society. The group is dedicated to preserving these links with the past and ensuring they aren’t discarded like other bits of bygone Britain, such as red phone boxes.

Fiona is a Carlisle city councillor for the Stanwix and Houghton ward. The Newcastle / Carlisle stone is on Brampton Road: part of her patch. She has been interested in milestones for about four years.

“I’ve got a lot of weird obsessions like that,” she says with a smile. “When I first became interested my husband was seriously concerned! I’ve got a long-term project trying to get Brampton Road cleaned up. I used some of my small-scale community budget for the milestone. It cost £430. I’d like to see other councillors do this. It does tidy up an area.”

Terry is an artist who, before 2013, painted only in oils. He then decided to restore the traditional fingerpost highway signs in Scaleby, near his home.

This led to work for parish and town councils on signs and milestones as far away as Keswick and west Cumbria.

He has restored more than 50 milestones, including the one on Brampton Road. “I’m just interested in preserving heritage,” he says.

This is more challenging than it might sound. The Milestone Society says about 9,000 stones survive throughout Britain - fewer than half the number there used to be.

During World War Two many were removed, buried or defaced to avoid aiding a German invasion, particularly in the south of England. Not all were replaced.

Many milestones were thrown away as roads were widened, or destroyed through collision damage. “Some are stolen,” says Terry. “They can’t sell them on eBay - it’s Crown property.

“I know of two that have been removed when they were straightening the road. Two miles from Thursby roundabout there’s one in front of a farm. That’s now 200 yards further back than it used to be.

“The contractors who were straightening the road were going to take it to landfill. The farmer said ‘Can I take it?’ He put it in his garden. I knocked on his door. It took me a year to persuade him and his wife it should be on the other side of the wall so the public can see it.”

Terry has found half a dozen milestones. After decades of neglect they can become severely overgrown or even buried. Ordnance Survey maps show where they should be.

“The best time to look is in winter when the vegetation has died back,” says Terry.

One of those he discovered was hidden in the ground at Crosby Moor, on the A689 near Crosby-on-Eden. He has immaculately restored it. The stone is painted white and the cast iron plates are black.

That is one of several which remain between Carlisle and Brampton. The A595 from Thursby to Cockermouth is another stretch of road with many surviving stones.

The A689 and A595 both follow the line of Roman roads. Milestones stem from Roman times, when vastly improved roads were laid to move soldiers and supplies quickly.

Distances were measured to aid timing and efficiency. Every 1,000th double-step was marked with a large cylindrical stone.

Just over 100 Roman stones survive outdoors in Britain, including one near Kirkby Thore. Others are in Carlisle’s Tullie House museum.

From the 1700s until the 1840s roads called turnpikes were built, funded by groups of local worthies called turnpike trusts. They charged tolls for using their roads.

Milestones became compulsory on turnpikes to inform travellers of distance and direction, helping coaches keep to schedule. As rail travel became more widespread, turnpike trusts disappeared: followed by many milestones.

Milestone Society members are not the only ones keeping this quirky example of British heritage alive.

“People are very helpful,” says Terry. “Some have taken it on themselves to tidy them up. Often they don’t know they are there until they’ve been uncovered and restored. If a parish council has funded its repair, the council is then likely to take an interest in keeping it looked after.”

The Brampton Road milestone needed a lot of TLC. Until a few months ago it was unpainted and covered in moss. Its metal plate had been stolen.

Terry spent a few hours cleaning the stone and about 20 minutes applying each of several coats of paint. He arranged for new cast iron plates to be made at a foundry. Now it’s been transformed from eyesore to asset.

Many Cumbrian stones follow the Brampton Road design. Terry prefers them to those north of the border. “They’re very boring, a lot of them in Scotland. They’re usually granite. Very simple.”

Whatever their appearance, milestones can still lift the spirits of walkers trudging to their destination. Cyclists too, says Terry. “They make it a point of interest: ‘Let’s see how many milestones we can find.’”

Fiona has had her “weird obsession” questioned by numerous people.

“They say ‘What’s the point? We’ve got GPS now.’ But they wouldn’t say ‘There’s no point to Hadrian’s Wall now - it’s not keeping the Scots out.’ “It’s more a historical interest. People are interested in the lives human beings used to live.”

Terry adds further historical perspective. “They were put down before the train was on the tracks, never mind the car.”

And there is a modern twist. The Brampton Road milestone is a Pokéstop: one of the locations used in mobile computer game Pokémon Go. Milestones remain the subject of real-life treasure hunting too. Fiona says: “Terry and I have been looking for one that should be outside Drawdykes Castle [at Linstock]. We can’t find it.”

Is it still there, hidden from view, or has it been displaced from its ancient sentry post? Enough intrigue... ask Terry how he feels about methodically keeping the past alive and his reply is suitably understated. “I was really excited when I first started. I just keep it quiet now. I just do it, and that’s it.”