Look at those joints, says Peter Stott. Medieval joints. There is only one parish church in England that has joints like that, he tells me. Green oak. All pegged in the proper fashion.

Then there's the stained glass in the belvedere, giant jujubes caught in a web of liquorice. 'Dalle de verre,' says Mr Stott proudly. 'That's what it's called. Only me and a couple of monks know how to make it.' The liquorice is in fact an exceptionally strong resin, mixed with marble dusts.

We are looking at his gatehouse, the culmination of many winters of building. An arcade of arches, started in 1985, finished in 1987, now runs along the back of his cottage and barn with a gallery running along the top of them, finished with a pergola roof. Underneath is a big, irregular pool surrounded by huge boulders and crossed by a curved bridge. Taken as a whole, the effect is remarkable.

Remarkable, but illegal. Peter Stott is a man who cannot pass by a heap of spare stone without dreaming of a folly, so he never stopped long enough to ask for planning permission. The Case of the Melkinthorpe Gatehouse has already filled an inordinate number of files in the planning offices of Eden District Council at Penrith, Cumbria. As a saga, it has much in common with the equally long-running Battle of the Shark in Oxford. There the shark, displayed on the rooftop of a suburban house, won the day. The gatehouse controversy has yet to be resolved.

The Stotts came to Melkinthorpe just over 10 years ago, when Peter and his wife, Briony, took over a barn and the rundown cottage next door, Larch Cottage, which was once the home of Cumbria's last highwayman. They cleared out the rotting tractors from the few acres behind the buildings and started up as nurserymen. They took on several school leavers and turned them into skilled propagators. They built up a thriving small business. Behind the barn and cottage Mr Stott started building, a project for each winter: arches, more arches, galleries, curtain walls, pillars. And then the gatehouse, his piece de resistance.

The path that led Mr Stott to this present destiny in a Cumbrian village is not easy to follow. He can produce a past for every occasion. You want an art student? You got one. You want a ballet dancer? Here he is. He has also worked for the RSPB, protecting golden eagles and peregrines. His father was a stonemason. That at least seems vaguely relevant to the present drama.

Why Mr Stott builds with such fervour, he does not know. 'It's just all in my head,' he says. 'And it has to get out.' The problem for Eden District Council has been that all these buildings have been getting out without the benefit of their advice and approval. The gatehouse was the final straw.

It sits in the middle of a curtain wall (the project of '85) which stretches from the end of Mr Stott's house to the boundary wall. It provides a theatrical entrance to the nursery, which sells herbaceous plants, alpines and old roses, most produced on the premises.

The entrance leads through an old arch of red sandstone rescued from a crumbling barn in Kirkoswald, Cumbria. 'A complicated arch,' says Mr Stott. 'Four centres of gravity. All arches have their own mathematics, you know.' And then he whisks you on, like a conjuror not wanting you to understand too much about his tricks.

Underneath the arch, stairs lead up to a timber-framed room, about 12ft by 14ft, jettied out slightly over the base. The walls are built up with panels of lime plaster, pargeted outside, plain inside, then topped off with square-paned windows, bordered in stained glass. A tiled roof sweeps up to the final conceit of the small belvedere topped with a clock.

Mr Stott's buildings may be extraordinary, but as far as the planning authority is concerned, that is neither here nor there. It is using several different kinds of ammunition to try to blow them up.

First, there is the tricky matter of listed building consent. Larch Cottage was listed as a Grade II building in 1987, four years after the Stotts had begun their restoration and additions. The curtain wall of which the gatehouse now forms part was built in 1985. Is the gatehouse therefore part of a listed building or not? There have been several shifts of opinion on this. The current planning view seems to be that even if it is not, it has a major impact on the setting of the listed cottage adjoining; either way, it would have required listed building consent.

Just recently, the planning department has turned its attention to the question of what is or is not a garden centre. A garden centre, in planning terms, is a different creature to a nursery, which is what Mr Stott has got planning permission for. They think that though he may have started off with the one, he has now got the other, because he sells pots as well as plants and gives people tea and cakes on his balcony. Mr Stott thinks he is doing the same as he has always done.

Public opinion is overwhelmingly in favour of Mr Stott. The Cumberland and Westmorland Herald recently printed an entire page of readers' letters in his support, after Eden District Council had slung out his application for retrospective planning permission and listed building consent for the gatehouse.

'Well, it's a gut reaction to a man who has worked hard and built up a good business, isn't it?' says Alan Hunter, one of the planning officers involved in the case. 'But that does not alter the fact that there have been regular breaches of planning control. I have said to Mr Stott that I am not averse to the idea of a gatehouse structure in principle. There are many local examples that he could have drawn on in respect of design and materials.'

But Mr Stott is an original. He doesn't draw on local models. Mr Hunter may find that a problem, but he doesn't knock the craftsmanship. 'Yes,' says Mr Hunter carefully. 'As an exercise in timber framing, Mr Stott has shown an understanding that does credit to him.' In truth the gatehouse, unplanned, has turned out rather better than many local buildings that have had the full benefit of planning permission. But the unspoken message is this: if the authorities allow the gatehouse, what is there to stop others from flouting the law? This is also the argument of local objectors (there are some, but they do not wish to be named).

Other people have, sometimes expensively, to toe the line with respect to planning law. Why shouldn't Mr Stott?

There is also the question of disturbance. Melkinthorpe is a small place at the end of a no-through road. A few residents - very few - resent the fact that, willy-nilly, they have become part of the nursery visitors' Sunday entertainment.

Why, you may ask, did Mr Stott not apply for planning permission before he started on his gatehouse? Because, he says, ingenuously, he did not think he needed it. Nor can you imagine this latest addition to his vision of Byzantium going down well in the council chamber at Penrith. 'It was just done for sheer love of building,' he says. 'All this fighting saps your creativity. It's such a waste.' This week the authority has served one enforcement notice to demolish the gatehouse and another demanding that the Stotts reinstate the nursery to its former use, which in effect would close it down. Mr Stott is appealing. A public inquiry is scheduled for the beginning of February.

Meanwhile, the district council has given outline planning permission for a 350-acre holiday village in woodland at Whinfell, only a few miles from Melkinthorpe. To an outsider at least, this seems a far more dangerous serpent in Eden than Mr Stott's gatehouse.

(Photographs omitted)