Killua Castle, a gaunt ruin outside Clonmellon, Co Westmeath, lay abandoned - then Allen and Lorena Krause came from Mexico (via London) to rescue it. Why? They tell Robert O'Byrne

"This is the project of my life," says London-based banker Allen Krause of Killua Castle and its restoration. Then he qualifies his remark by admitting the work could yet take several lifetimes, so vast is the challenge posed by Killua.

An enormous, gaunt ruin sited on undulating ground outside Clonmellon, Co Westmeath, the original house was built in the mid-1780s for the Chapman family.

Cousins of Sir Walter Raleigh, they had first settled in Ireland thanks to his patronage, an act later commemorated by the erection in 1834 of an obelisk to Raleigh that still stands in the old demesne.

The Chapman association with Killua came to an end early in the last century. The seventh and final baronet, Sir Thomas Chapman, left his wife and daughters to live with another woman; one of the five sons from this union was T E Lawrence, otherwise known as Lawrence of Arabia.

Following Sir Thomas's death in 1919, Killua passed through several owners. Its fittings were sold in 1944; not long after, the castle's roof was removed and its lead sold. Until bought by Allen Krause and his wife Lorena in 1999, Killua stood exposed to the elements, a prey to vandals who even stripped away some of the cut-stone window entablatures.

"There was a huge sycamore tree growing in the basement," Allen remembers. "It came up through what had been the diningroom and was reaching to the sky beyond. All the floors had collapsed; quite frankly it was scary. On the one hand, the house is magnificent and wonderful but on the other it was in an unbelievable state of disrepair."

So why did the Krauses - both of whom are Mexican and have no family ties with Ireland - decide to rescue Killua? "I came to Ireland many years ago," he says, "and just fell in love with the country: the history; the unspoilt countryside; the friendly people."

So much in love that he eventually decided to buy a place here. "We were looking for quite a long time. At the time we were living in New York but every holiday we'd come over to Ireland and be hunting around."

Their hunt led them to Killua, a house that in its original incarnation was a typically symmetrical late-18th century classical residence, of three storeys and with a three-bay curved bow overlooking the parkland and lake. Possibly designed by Thomas Cooley, this house underwent a radical transformation from 1821 onwards when in keeping with current tastes the second baronet decided his home should look like a castle.

Towers, battlements and castellations were added, gothic archways and trefoil decoration introduced. The architect responsible is believed to have been James Shiel, whose other commissions in the same part of the country include Tullynally, Knockdrin, Dunsany and Killeen Castles.

Within 30-odd years, Killua had been turned into a fancifully asymmetric building, although beneath the romantic additions it was still possible to detect the original structure's form, especially in rooms such as the oval saloon and octagonal entrance hall, where delicate neo-classical plasterwork was retained.

After six decades of exposure to the elements only a few traces of that craftsmanship can be found and an awful lot of conjecture is required to conceive what Killua must have looked like when owned by the Chapmans. And to imagine that it can possibly be recreated. Understandably Lorena Krause was less than enthusiastic at the prospect of taking on this task.

"I'm amazed we're still married," jokes her husband, although he insists that now both she and their young children "absolutely love it. Lorena pays all the bills and sometimes asks why are we doing this. But then she visits Killua again, feels the magic of the place and comes back to London loving the house even more."

Still, it's hard to disagree with his proposal that in order to restore Killua "you have to be a complete madman". When the Krauses first saw the house, its condition appeared so perilous that even short-term survival was open to question. "What we did before buying," he says, "was engage the services of a structural engineer to find out were the walls crumbling or would they hold."

The eventual report said they would, although the entrance façade had to be propped up by a large steel structure while work was done elsewhere on the building. An enormous crane was needed to lift workmen over the roofline and allow them to take down the chimney stacks without causing internal walls to collapse and similarly one of the ornamental turrets required support lest it crumble and bring down at least a quarter of the building.

"We'd a lot of sleepless nights during that period," Allen Krause remarks. "Even getting insurance was a big deal."

Six years on, while the exterior is still smothered in scaffolding, Killua is now safe and in no danger of falling down. It has a sturdy new roof and the first and second floors are back in place. "I certainly didn't have the funds to take on such an endeavour and complete it all at once,'"says Allen, who prefers not to divulge how much the restoration has so far cost him. "When I first sat down with the architect and builder to budget what was needed, we came up with a figure that was twice the amount we've actually spent.

"Each stage of the process has been self-contained and quantified. Every single task was a small step, so it never seemed daunting to anyone involved."

What's next? "I'd like to finish the exterior entirely," he says. "Hopefully that'll be completed by the end of this year. Then we'll turn our attention to putting in services like electricity, septic tank, plumbing, all that sort of stuff."

Initially he plans to focus his attention on the latest section of Killua, a wing to the east built between 1830 and 1858. "I intend to make that into a house within a reasonable period of time. Two years should see us living there, then I'll start putting windows in the rest of the building, making it all watertight. The restoration of the main block can be done very gradually; the plan is to tackle one of the ground-floor rooms per year." The Krauses regularly fly over from London to see how their project is progressing, often staying locally with friends such as the Nugents of Ballinlough. They're in no hurry to see Killua finished. "My philosophy," says Allen, "is that it's better not to rush, always allocate more time than you need and do the thing in a way that you can actually achieve your goal. In a way, it's irrelevant whether I get it all done or not. That can be left to my children, or grandchildren."