"We bullied the children into believing it was going to be a fabulous adventure, but after a weekend of washing over a standpipe and using a bucket to flush the loo, they weren't convinced," says Mrs Walsh. "It was pretty awful," she admits.
Indeed, four years ago, Dancers Hill House, with its 18 acres of gardens and fields, was short on all home comforts. Most of the running water came through the roof. "All the lead had been stolen and the rain had soaked all the timbers. The plaster was loose and if you didn't walk round with a hard hat you'd be knocked unconscious. The first thing we had to do was to make the house watertight."
So bad was the house, in fact, that Melanie and her husband Nigel chose not to tell the rest of their family of their plans to move there and restore it. "Never in my lifetime", were the words of an aunt, when she finally clapped eyes on the project. She was wrong. Within a couple of years the splendour of the Grade II-listed house had become apparent. Rooms were unboarded to display the proportions of their 18th-century origins, period features were saved and painstakingly copied where they had decayed beyond repair. At the same time, the history of the house was gradually uncovered as the Walshes burrowed into cellars and stables.
As Melanie drives us through Hadley Green, Barnet, on a mini-guided tour her love affair with houses, as distinct from property, is obvious: "The one that looks like a church was Spike Milligan's house; this is the oldest cottage in the village; I'd love to buy that house - gorgeous, isn't it?"
It is not a new interest. "I got the bug when I was 11. My parents wanted to move and I was fascinated by all the house details that kept arriving. Ever since then I have spent most of my spare time looking at houses. My husband is just the same. That's why we are selling our house now: we need the challenge of something new. I suppose some people would think we were mad."
Melanie Walsh has an infectious enthusiasm. At Dancers Hill she points out the curious arched passage way at the back of the drawing room that had been an open loggia until incorporated into the building, and that the back of the house is higher from the ground than the front, to stop servants watching the comings and goings in the drive. We look at a vast bedroom with a study, that had once been five dark and poky rooms. In the library, home to the family's myriad collections of anything from Dinky cars to unopened Batman packs, she points to a fireplace - "We had to go to Huddersfield for that" - and an ornate ceiling rose: "The excitement when we knew we could save it". Yet, in the restored conservatory, imitation flowers replace the real thing. "They all died during a hot spell when we were away", explains Melanie.
She was unwilling to say how much all this restoration work cost, but Nick Staton, the agent handling her property, said that today a house like Dancers Hill, bought in a very run-down condition, would go for about pounds 750,000.
In the basement, work is under way to make the enormous original kitchen habitable, with its stone flagstones and ancient range: "It's really so that Nigel can cook - he's marvellous at it - and chatter to people at the same time."
The house is, despite long hours with conservation officers and builders, first and foremost a family home. "We cherish its history, but it's not a museum piece," says Melanie Walsh, firmly.
For most of the time it is overrun with friends of her sons, who find themselves in a child's paradise. Where the formal garden ends, the fields and wooded wilderness begin, and a football pitch has even been carved out of a clearing. There are stables, used for the filming of Lady Chatterley's Lover, a 300-year-old cottage, and the remains of a 19th-century swimming- pool, now home to a family of moorhens.
"It once took me two hours to find my sons during a game of hide-and- seek. We have strict rules now."
So won't the family miss all this space? Melanie is unrepentant. "They understand that we need a new challenge. It will be very exciting. In fact, I've been looking at this old asylum ..."
Dancers Hill House is on the market for pounds 1,350,000, with Statons, Hadley Green (0181-449 3383).Reuse content