My offering this week comes from the place Percy French surely had in mind when he wrote "where the dark Mournes sweep down to the sea". Great mist-topped eminences are offering tantalising promises above us, so everyone is eager for the off, but getting through Newry has sundered our convoy. Eventually, the remaining cars arrive and soon we are away through the ancient woodlands of Donard Park. Sylvan paths tagging the rushing water of the Glen River convey us to open mountainside. Here, we pause as one to banquet on the spectacular views back over Newcastle, Co Down, which justifiably styles itself the "activity resort" of Northern Ireland.

It is important to push on, however, for we have a mission to accomplish. Taking part on the 18th annual Autumn Charity Challenge, our aim is raising funds for the Suirhaven Cancer Charity. The challenge set for us is to stand on the highest summit in Ulster. So it's on through wilder lands as the paths dogleg upwards towards the broad col between Commedagh and Donard.

Here we gain Ireland's answer to the Great Wall of China. Roller-coasting over 15 summits and for 22 miles, the Mourne Wall was built about 100 years ago to enclose the water catchment of the Silent Valley Reservoir. Made obsolete by modern water purification techniques, the main use for this remarkable edifice these days is as a convenient handrail for walkers navigating the high summits in mist.

An expansive prospect now unfolds as we ascend left by the Mourne Wall. Laid out before us is the outrageously beautiful Annalong Valley and its great necklace of surrounding peaks, including the humpback outline of Binnian and the unmistakable twin tors of Bearnagh. Directly below is the Brandy Pad, an old smugglers path redolent of more lawless times when it was used to transport illicit cargos of liquor from the coastline for distribution inland.

It's a steep flog upwards from the col, not made easier by the fact that a claggy mist has now descended like a giant theatre curtain. Everyone is glad when the sturdy tower on the Mourne Wall, marking Donard's summit, looms out of the mist. In a biting east wind we shiver our way onto the top and congratulate each other as we take cover behind the Mourne Wall. On previous visits to Donard, I had banqueted on sublime views extending to Wales, Scotland and the Isle of Man, but today we see nothing but the opaque surrealism of an Irish mist.

We could have created a very fine circuit from here by descending south along the Wall to the col with Rocky Mountain and then following the Brandy Pad south to Bloody Bridge carpark, which lies 3.5km south of Newcastle. But this was the day of the All-Ireland football final replay and a group of Mayo supporters among us were inordinately anxious to get back to our hotel. So we retraced our steps down by the Mourne Wall and then along the Glen River, stopping, only briefly, to feast our eyes on a sublime ocean view which now included the Isle of Man, while as yet unaware that the curse on Mayo football is set to persist for another year.

WALKS SLIEVE DONARD, CO DOWN

Starting point: Donard Park, which is located near the centre of Newcastle, Co Down.

Time: About 4 hours.

Suitability: Steep ascent that otherwise presents little in the way of navigational problems. Route is entirely on tracks and, at higher altitude, follows the handrail of the Mourne Wall.

Map: OS Northern Ireland; Mournes map, 1:25,000.