ORIENTEERING is definitely the most physically demanding of all the sports I've had a go at so far in this series - and this time, much to the amusement of my colleagues, there was no way I was keeping my tie on.

Anticipating that the experience might involve getting cold and wet, I made sure I was protected by a couple of layers of warm clothing as I set off for Eston and the start of an event organised by the Cleveland Orienteering Klub (or Clok for short).

The morning was fairly bright and miraculously dry as I parked my car and went in search of the club chairman, Peter Archer, who had agreed to take me round the course.

Before we set off, Peter explained how an event like this is organised. There are several courses of varying length and technical difficulty and competitors can choose whichever suits them best.

I was immediately struck by the wide range of ages and abilities which the sport caters for. There was a string course for younger children aged up to eight or nine which is designed to introduce them to the principles of orienteering.

The youngsters simply follow a piece of string, finding various symbols along the way which match those on a sheet they are given at the start. They also get used to the terms used to describe locations on a course.

There was also a Trail O course, which is suitable for people with disabilities or mobility problems.

The main course was laid out over the hills and scrubland of Eston Nab, where the various checkpoints, called controls, had been identified by a planner around three months earlier.

This was a badge event, with the various courses divided according to age groups. Some events are colour-coded, with different colours representing varying degrees of difficulty.

Competitors first have to go through registration and pay their entry fee - here it was £5 for seniors and £2.50 for juniors, students and unemployed.

Everyone is given a detailed map with their course marked on it, together with the number and description of each control location, and a start time. Compasses are not supplied.

The controls, made visible by orange and white markers, each have a pin punch with a unique pattern which is imprinted onto the paper carried by the orienteers to prove they have visited each control.

Peter and I were following the men's over 50s course, around two and a half miles in length.

Soon after setting off at a steady run, we were slowed to walking pace by a steep climb. Halfway up we were overtaken by a young girl, who was running despite the gradient.

"Puts us to a shame a bit", remarked Peter, but then he added: "Mind you, that is the ten-year-old girls' British champion".

Having reached the top and found our first control, Peter worked out a route to the next control and we set off at quite a fast pace across rough terrain.

The area was criss-crossed by a confusing number of paths of varying size and Peter had to be accurate with the map and compass to keep us on line. Part of the skill lay in recognising on the map which areas would have to be skirted around.

I was having to work quite hard to keep up with Peter, who first took up the sport in 1988 and was clearly fitter than the average 54-year-old.

Although we followed a path whenever possible, we were also crossing areas of heather and rock-littered heathland which made running difficult.

At one point, we splashed our way through a short stretch of marsh, but I soon recovered from the shock of having my feet immersed in icy water.

My companion found each of the nine controls without too much difficulty and we arrived at the finish just over an hour after setting off.

Peter said he would normally expect to go round in about 50 minutes, but obviously he had taken more time than usual to explain to me the mechanics of how he planned a route to each control.

As Peter explained, orienteering is a sport which can be enjoyed at many different levels. For the elite competitors, who are also often experienced cross country runners, it is a serious test of their stamina and navigational skills.

But it can also be enjoyed as a family day out, combining fresh air and healthy exercise with a touch of adventure.

Peter, who is based at Mowden Hall in Darlington as an operational researcher for the Department of Education, first became involved as a way of spending time with his two teenage sons who had done some orienteering at Northallerton School.

He said: "I enjoy the physical exercise and you can go at your own pace. If you want to try to win a class, you can go for it, but you can set your own goals."

The sport developed from the training activities of the armed forces in Scandinavia more than a hundred years ago, but has only been established in this country since 1968.

The various clubs organise competitions throughout the year and permanent courses have been set up in schools and urban parks such as Stewart Park in Middlesbrough.

Many orienteers first become hooked at school or university, but there are opportunities for adult beginners to take up the sport.

They can find out more details by visiting Clok's website at www.clok.org.uk or by contacting Peter Archer on 01609 882420.