On a swing suspended from an old oak tree in the park of a Wiltshire estate, I am swaying above a lattice of vivid red steel diagonals, cut, folded and painted as if they were paper. Michael Bolus’s geometric abstraction appears to hover weightlessly over the ground, like a drawing in space. Across the lawn, David Annesley’s large yellow triangle with undulating sides intersects with a white circle – a dynamic, candy-bright work from 1966 whose free floating forms also seem to deny the materiality of its welded steel construction, insouciantly rejecting the volume and solidity of traditional sculpture.

The swing soars and the view takes in verdant pasture with cattle strolling past Barry Flanagan’s 30ft-high leaping bronze hares, and a walled garden housing pop artist Jim Dine’s “King Parrot” perched on a bronze heart. In the distance, a lone Antony Gormley figure looks out to an infinity of time and space; beyond a bluebell wood the rusty corten steel of Anthony Caro’s monumental “Millbank Steps”, last seen when it was inaugurated in Tate Britain’s Duveen galleries four years ago, is silhouetted against the sky. I swoop back to the ground and almost hit an elegant, forceful, grey-haired woman in tweed skirt and sensible shoes who is striding towards me. It is a perfect, on-site introduction to Britain’s leading sculpture collector and dealer, Madeleine Bessborough, who in 1994 relocated her London gallery to her country home and turned Roche Court, near Salisbury, into one of the most spectacular places to see art in Europe.