Underneath the spreading chestnut trees

It may be centuries before the words National Forest engender the same arboricultural rapture as the words New Forest, but just eight years after Michael Heseltine pressed in the first sapling in that wave of post-Rio Summit euphoria, the forest has become England's most ambitious environmental project of the new millennium. Quietly transforming areas of Leicestershire, Derbyshire and Staffordshire, the blend of new planting and ancient woodland will together form the largest new expanse of forest we have seen for 1,000 years.

It may be centuries before the words National Forest engender the same arboricultural rapture as the words New Forest, but just eight years after Michael Heseltine pressed in the first sapling in that wave of post-Rio Summit euphoria, the forest has become England's most ambitious environmental project of the new millennium. Quietly transforming areas of Leicestershire, Derbyshire and Staffordshire, the blend of new planting and ancient woodland will together form the largest new expanse of forest we have seen for 1,000 years.

The 200 square mile National Forest takes in a few large towns and several small villages, intermittently pretty countryside, surviving scraps of the ancient Needwood and Charnwood, and a landscape scarred by mineral extraction and spent coalfields.

To describe the enterprise in architectural terms, at the same stage in its building, York Minster was about five per cent complete. I would have been standing on a dusty floor, among robed architects unfurling their parchment plans, while master masons swarmed up wooden scaffolding set against the head-high brickwork. That analogy goes only so far. Would they have let day trippers to York in 1225 walk around and see the great creation, roofless but rising above their heads? Probably not. But up to 2,000 visitors a day are already enjoying this new lowland forest and the first fruits of the huge planting of 30 million new trees.

I started at the recently opened Heart of the National Forest Visitor Centre at Moira, near Swadlincote in Leicestershire. This was a bleak and derelict place eight years ago, part of a whole swathe of the Midlands devastated by the closure of coal mines. Now there's enough here to entertain visitors for half a day, even when there isn't a conservation event hosted by the forest rangers or a performance - which could be jazz or folk music, a brass band or a play - at the outdoor amphitheatre.

Moira is back on the tourist map after 150 years. In the year of Waterloo, miners discovered a saline spring 600ft down. A spa was developed on the surface, with a hotel and baths, but the visitors decided they did not enjoy the view of the new coal mine. The whole enterprise moved to nearby Ashby de la Zouch, including the spa water, which was transported by a canal that is now being re-created.

I strolled across what was once a blasted old spoil tip; it now supports an embryonic forest where nine trees out of 10 are thriving . At the large visitor centre, I toured the thoughtful exhibition and glanced at the shop, where almost everything on sale is made of wood. This is the antithesis of the tacky gift shops found in many other attractions. There is also a play park and a second shop selling fences and garden furniture. But trees are an invitation into the open air, so after a quite acceptable tomato and rocket quiche in the lakeside restaurant, I hired a bike.

The Ashby Woulds Heritage Cycle and Walkway, which follows a disused railway line leading from Moira, connects several emerging features of the new forest. I stopped at the Moira Furnace, a relic of the early 19th-century iron industry and part of the view that offended the original spa users, then pedalled east. Here the forest is coming together like a huge jigsaw, the many pieces located on road verges, fields, school playgrounds and old industrial sites.

A squirrel will never be able to scamper over an unbroken canopy from Lichfield to Leicester. This fits with the traditional definition of a forest, a "covering of trees" and "woody ground" serving many purposes. But, eventually, a third of the land area, 13,500 hectares, will be under trees, mainly broadleaved. Planting continues apace.

Trails lead off across farmland which may not have seen a bursting bud or a falling leaf since the original wildwood was hacked down. This land now supports thickening stands of dogwood, sweet chestnut and hazel. Swallows skim over ornamental lakes fashioned from colliery flashes. Twenty minutes on from Moira I found the Woodland Trust's Willesley Wood, the forests's oldest plantation. Its oak trees are well above head-height. This is how the New Forest must have looked early in the 12th century when it was a mass of saplings.

Sadly, somebody in control has stalled on authorising the Ivanhoe Line, the proposed rail link through the forest from Leicester to Burton on Trent. There aren't many buses. So the awkward truth is that, if you don't cycle or ride a horse or take a canal boat, you have to get about - unsustainably - by car.

I drove across to Rosliston to witness the triumph of the protective Tuley tube - in which tender saplings are encased - over the old seed drill method of growing trees. Forest Enterprise bought this 154-acre farm and is smothering it with trees. Outside the interpretation centre a huge wood bas-relief is crammed with every imaginable common woodland species. At Norris Hill I found the tree that marks the forest's exact centre. After that it seemed sensible to seek tree number 1 million, planted in 1996. It is in the middle of Burton, in the grounds of the Bass Museum. I inspected the feathery, flimsy rowan through the railings. Do they refresh it with beer?

Burton is too busy, and big, to be "Forest Town". Ashby de la Zouch, 10 miles east, surely takes the title by default, with ready-made woodland connections. Guess who - not Robin Hood - is to be found on the local council's logo? I spotted Ivanhoe's charging likeness on a civic litter bin. Visitors will also be pleased to find that the planners have preserved enough of old Ashby to provide a convincing backdrop for a BBC2 costume drama.

Just above Woodhouse Eaves on the fringe of Leicester, I discovered the forest's definitive eco-statement, the Native Tree Collection. On a sloping meadow on the easternmost edge of the forest are planted all 28 species that colonised Britain after the Ice Age. In other areas of British wildlife there may be gaping holes caused by extinction. But here our complete stock of trees has been called up out of the past. It is an eloquent punctuation mark in a National Forest that represents the greatest repair job carried out on the landscape in the past thousand years.