News: Stirling Prize judge Tom Dyckhoff has spoken of being "punched in the gut" by the house-inside-a-castle that clinched the award last night, although its architects missed out on the usual £20,000 cash bounty, as organisers RIBA failed to find a sponsor.

"It ticked all the criteria of the Stirling Prize, which is a list as long as your arm," Dyckhoff told Dezeen. "But it also punched you in the gut in a way that is really hard to explain."

The renovation of Astley Castle in Warwickshire by Witherford Watson Mann is the first individual house and the first restoration project to win the award, which goes to the building deemed the greatest contribution to British architecture in the last year.

"It's really easy to be romantic about ruins," added Dyckhoff, journalist and co-presenter of BBC's The Culture Show. "You know everyone loves a ruin and its history, particularly in this country. But the building was utterly magical. It was intellectual, it was clever, it was incredibly pragmatic, it was affordable, it was clever right the way down to the smallest detail. It had a great concept and it had the great details, and that is a really winning combination and it was magical and romantic."

However the winning architects missed out on the £20,000 cheque, which has been handed to every Stirling Prize-winner since the award's inception in 1996.

"We thought we would find a sponsor but we didn't," said RIBA Head of Awards Tony Chapman. "It's sad". Chapman said he personally called all the shortlisted architects to explain that there would be no cash prize this year.

Architect William Mann nonetheless described the win as "fantastic" and said he believed this year's shortlist represents a "return to the values" of architecture. "[The project] has been an opportunity to communicate the values that we're interested in," he said.

Stephen Witherford added: "I believe very strongly that old and new buildings work together. Sometimes we try to separate them, but there's a happy coming together here."

The project was initiated by architectural charity The Landmark Trust, who launched a design competition for a holiday house that could be created within the decaying twelfth-century structure.

"It was really exciting for us to take the ruins of a historic building and to do something completely new in it," said Landmark Trust director Anna Keay. "Normally we follow a relatively straightforward approach with preservation jobs, but to have resolved upon something more adventurous and to find Witherford Watson Mann to realise an adventurous approach to historic building was to us, as the clients and The Landmark Trust, incredibly exciting and I hope this has given inspiration to others."

The 2013 RIBA Stirling Prize was awarded last night in a ceremony at the Central Saint Martins campus in London. Read more about the project in our earlier story.