Small man, big art, even bigger park

Wilfred Cass is a small man who loves big art, the bigger the better.

This weekend he celebrated his 80th birthday by mortgaging his home, to add another five acres and a vast indoor sculpture gallery to a unique sculpture park.

"Big hole, isn't it?" he said, rubbing his hands in glee and dancing on the edge of the precipice.

He relishes monumental British sculpture, the kind which costs a fortune to make, move, or buy. At present he has 62 pieces, worth £3.7m, in his front garden.

In the 10 years since he and Jeanette, his wife, created Sculpture at Goodwood, on land carved out of a wooded corner of the Goodwood estate in West Sussex, more than 100 major pieces of sculpture have been commissioned - and mostly sold.

"What he has done is very good for English sculpture," said Sir Anthony Caro, who celebrated his own 80th birthday earlier this year. "He's giving us a place to show, and people a chance to see them, instead of pieces just going straight into store. I get on very well with him: we've met each other's match."

His own Goodwood Steps was the only piece so enormous it had to go by the roadside, outside the gates: the risk of somebody stealing 50 tons of welded steel, 20ft high, was remote.

The artists are an inventory of late 20th century British sculpture, studded with Turner nominees and winners: Langlands and Bell, Turner shortlisted for this year, David Mach, Bill Pye, Tony Cragg (who gets the first one-man exhibition of 12 massive new pieces in the space), Richard Long, Andy Goldsworthy, Rachel Whiteread, and Eduardo Paolozzi.

In most fine art circles the simple question "how much?" will provoke a hiss of distaste and an answer as squirmy as when trying to find out the true price of a fitted kitchen.

Visitors to Sculpture at Goodwood, however, are given a handsheet - with prices. They range from £0.5m for a murderously spectacular mobile by Lynn Chadwick, which the artist only saw as a model before his death last year, down to £4,000 for a cast iron bollard in the shape of a penis, by Sir Antony Gormley.

Everything down to the elaborate gates (Wendy Ramshaw, £40,000) is for sale. Marc Quinn's The Overwhelming World of Desire, a 20ft steel orchid currently looking like a giraffe in a window box outside Tate Britain, has just been sold, for £200,000, to a towering City corporate headquarters.

Cass commissions the pieces, pays for the materials, and, when they are sold, shares the price between the artist and the sculpture trust charity - to make more pieces. "Wilf Cass funds ideas, that's what's brilliant about him," said the Irish sculptor Eilis O'Connell, whose Carapace (stainless steel and cable, 10ft tall, £80,000) cuddled into a hollow below the trees, is one of Cass's favourites. "Unless you get a commission, the sort of stuff I do is so expensive to make that it's really hard to get beyond the idea. I'm never that optimistic that my work will sell, but he is."

Cass came to England as a boy, when his German Jewish family got out just before the war, and spent a lifetime in art materials and formal dress hire. "The business back ground and approach are crucial," said his first curator, Anne Elliot. "It's very unusual in the arts. He's a very creative thinker, but he's very demanding; he thinks fast and he moves fast, and woe betide anyone who can't keep up."

Despite the mortgage, he has bought himself a birthday present: Hugo, a grasshopper-green telescopic forklift truck, which can lift a six ton sculpture or an entire forest tree.