"It's now six years since the National Trust's successful bid to buy a good part of Wales' highest mountain. The Save Snowdon appeal captured the hearts of hundreds of thousands of people worldwide, including the appeal's president, actor Sir Anthony Hopkins, who dipped into his own pocket to the tune of £1m to help buy Hafod y Llan farm.

At 4,370 acres (1,769 hectares) it must be one of the Trust's biggest farms and it is certainly our largest direct farming venture by far. It lies in the upper reaches of the Nantgwynant valley and rises steeply from a patchwork of level fields bounded by dry stone walls through rugged wooded slopes to the dramatic Cwm Llan and the summit of Snowdon itself.

The high profile nature of the appeal stirred up a debate about the whole issue of how best to care for beautiful places in our countryside. Articles appeared in national newspapers with headlines such as 'Snowdon doesn't need saving' and 'The peak of folly'. Those of us caught in this maelstrom of publicity had to work hard to explain what the catchy but misleading slogan actually meant. We struggled with the question, what difference can the Trust's protection actually make? So, now that the dust has settled, what difference have we made?

We gave ourselves a year's breathing space by letting the farm for 12 months to Richard Williams, who had sold the farm to the Trust. During that year we discussed the options for the management of the farm and finally took the decision to embark on the Trust's largest direct-farming venture. We also drew up a plan to restore the habitats of the farm.

For the first two years, under the direction of our farm manager, John Till, aided by two stockpersons, a conservation shepherd and the local estate team, we tackled the huge backlog of work to get the farm back into shape. Thousands of metres of dry stone walls and fences have been repaired or replaced, dozens of home-made gates have been hung and a farm trail has been created so that visitors can see for themselves the progress on the ground.

Sheep numbers have been cut by half to 1,600 Welsh Mountain ewes, and a herd of pedigree Welsh black cattle have been reintroduced to graze the mountain pastures. The farm has gained organic status and is part of the RSPCA Freedom Foods scheme.

One of the more radical aspects of our plan is the Cwm Merch Project, which is being partly funded by the Countryside Council for Wales and the Forestry Commission. This has involved enclosing a 500-acre block of the farm to encourage the development of heath and upland scrub whilst grazing it seasonally with Welsh Black cattle. This will be monitored to see if it's the best way to restore the biodiversity of areas that have been heavily sheep-grazed for generations.

Already, the changes in the vegetation of parts of the farm have been very noticeable. Heather is colonising areas that had been dominated by acid grassland for the best part of a century and the property's outstanding botanical feature, its area of juniper heath, seems to be responding well to the drop in grazing pressure. Coarse grasses, in particular mat grass and purple moor grass, are dominating some areas. Here, cattle have been invaluable in keeping grasses from becoming too rank whilst allowing heath plants to re-colonise.

The experience gained through running Hafod y Llan is being used to inform policy-makers and farmers, and draw up conservation plans for our tenanted farms."