Capper, Wilfrid Meredyth (1905–89), conservationist and creator of the Ulster Way, was born in Belfast on 12 July 1905, the second son of four children (two boys and two girls) of John Malcolmson Capper, a cotton yarn merchant, and Elizabeth Jane Capper (née Stewart); the family was methodist. After they moved when he was a young boy to Ballyholme, Bangor, Wilfrid attended Bangor Grammar School and then Methodist College, Belfast. Like his elder brother, Norman Stewart Capper (who was later a lecturer in chemistry at Queen's University, Belfast, before moving to England), Wilfrid graduated from QUB, and in 1923 entered the new Northern Ireland civil service. He worked in the Department of Education until 1941, then transferred to the forestry division of the Ministry of Agriculture until retirement as senior clerk in 1970.
In retirement Capper was able to devote himself to his true life's work: the protection of the Ulster countryside and heritage, and developing means by which more people would be able to access it. His own love of walking dated from schooldays; he was a member and one-time president of Belfast Rambling Club, and he was one of the founders of the Youth Hostel Association of Northern Ireland (YHANI). As Capper remembered long afterwards, in the 1930s it was possible to do things quickly, and after their first meeting, at Hallowe'en 1931, the new group opened its first hostel in time for Christmas, at Mullaghdrin in the Dromara hills. Some of the seven founders of YHANI pushed a handcart round Belfast, appealing for donations of unwanted furniture to equip the old farmhouse. Youth hostelling quickly became very popular, and in its heyday the association ran twenty-eight hostels. Capper was concerned that the unregulated spread of holiday bungalows and shacks (his name for which was 'sea shanties!') would spoil all of Ulster's coastline, and with YHANI colleagues organised a public appeal to raise £15,000 to buy White Park Bay in Co. Antrim. In 1938, after two years of fundraising, YHANI handed 180 acres of beautiful coastline over to the National Trust (of which Capper was also a lifelong member, and a committee member for forty-five years). In 1946 he helped with appeals to raise money to buy Collin Glen near Belfast, and to help Fred Storey purchase Coney Island in Lough Neagh; both properties were handed over to the National Trust.
Capper was concerned that contemporary economic and other conditions imperilled the survival of the beauty of the countryside, and realised that the authorities were at best ambivalent about imposing planning controls. He called a meeting on 27 September 1937 to set up a group to work on what would now be called conservation issues. The first council meeting of the Ulster Society for the Preservation of the Countryside (USPC) took place on 25 October 1937. Capper was honorary secretary for more than forty-eight years; R. H. Buchanan (in a foreword to the history of the society) commented that the society's history was the story of Capper's own life, and it is also the story of increasing awareness in the province of the importance of many heritage issues. The society's records document campaigns, exhibitions, publications and other projects which set the agenda for conservation in Northern Ireland for more than a generation and helped form public opinion on many aspects of heritage and environment. Capper and his associates campaigned for the protection of rights of way, for legislation to set up tighter planning controls on rural building development, for tree planting in urban areas, and against rubbish dumping in the countryside. The society's representatives (very often including the influential businessman and society president, Fred Storey (d. 1962), as well as Capper himself) were increasingly consulted on planning matters at all level of administration; they called for the provision of nature reserves, for a right of way along coastal foreshores, and for public ownership of the Giant's Causeway. Capper served for many years from the late 1940s on the Ulster Countryside Committee, which eventually oversaw the designation of a number of Areas of Outstanding Natural Beauty, and was later a member of the Northern Ireland Amenity Council. It was as a result of Capper's lobbying of road engineers that the landmark Scots fir trees lining the road at the Frocess, Co. Antrim, were protected; he also insisted that nineteenth-century milestones be replaced after road-widening schemes. At one planning meeting, Capper stated that the building of a road through the Lagan valley at Edenderry would only proceed over 'my dead body'; the beleaguered engineer was heard to remark that Wilfrid Capper's body would be a very poor road foundation!
In 1946 Capper walked the 200 miles of the Pennine Way in northern England. On his return home, he began to urge the establishment of an equivalent long-distance path in Northern Ireland, which he thought might link between existing youth hostels. Some initial planning was done with local rambling clubs, but the difficulties of organising such a venture were so considerable that it was not until after Capper's retirement that he was able to give it his full energy. In 1974 the USPC asked the Sports Council for a grant for a pilot scheme, and Capper was appointed footpaths officer, to plan a circular route to take in Ulster's most scenic areas. The original six-month scheme stretched to eleven years of (post-retirement) full-time employment; Capper did what he called 'the footslogging' – walking and driving over thousands of kilometres to test possible routes – and succeeded in negotiating access with hundreds of landowners and persuading local authorities to take responsibility for signage and upkeep. From 1979 the original route of approximately 540 miles (870 km) was officially known as the Ulster Way, and Capper was the first to walk the distance in its entirety. The route has subsequently been modified; in 2013, the combined 'quality' and 'link' sections of the revised route (which now includes sections in counties Donegal and Cavan) totalled some 625 miles (1,005 km), making it one of the longest designated walking routes in the British Isles. Capper's continuing enthusiasm for his project was such that in 1993, at the age of 88, he hiked the whole distance in thirty-two days. Part of the Ulster Way, in north Down, is named the Capper Way in his honour.
A rebranding and increased commercial marketing of the route as part of an 'International Appalachian Trail', announced in 2013, would almost certainly have disappointed Capper, who was strongly committed to an ethos of volunteering, local efforts and self-help, and to promoting a healthy lifestyle to be shared with others less fortunate. As early as 1926 he was involved with the Co-operative Holidays Association in Belfast, and established a local Boys Club which took boys from poor districts on walking holidays to the Mourne mountains. He founded and was chairman and vice-president of the Association of Boys Clubs of Northern Ireland, and was responsible in 1978 for setting up the Ulster Federation of Rambling Clubs. In 1932 he founded the Vegetarian Society of Ulster, and was its secretary for many years; he was also chairman of the Irish Temperance League.
Capper wrote Caring for the countryside: a history of fifty years of the Ulster Society for the Preservation of the Countryside (published posthumously in 1995), and many articles in magazines, journals, guidebooks and local newspapers. His sketches, maps and photographs were used as illustrations in others' books and in material relating to the Ulster Way. He was appointed MBE in 1975, and given the Sir John Hunt Award for services to the countryside. His wife Evelyn (née Thompson), whom he married in 1936, predeceased him, and there were no children. Wilfrid Capper died in a nursing home in Crawfordsburn, Co. Down, at the age of 93, on 27 July 1989, and was buried from Holywood methodist church.