The rain was bucketing down. Wearing wellies and sheltering under the largest brolly I could find, I sought out the 169 stone sculptures in the sixth on form exhibition at Asthall Manor, near Burford. And strange as it seems to say, it was wonderful! Dark grey stone glistening in the wet, the colours of lighter stones intensified beyond imagin-ation, runnels of rain adding patterning, the reflections on the darkest of them travell-ing round with me as I circled these marvellous works of art — and all nestling in the most verdant of English country gardens above the Windrush Valley.

There are 28 sculptors in this year’s on form, the sixth biennial exhibition of stone sculpture — the largest show of its kind in the UK, conceived and organised by Asthall Manor’s owner Rosie Pearson. Among them are established artists such as Bridget McCrum, Peter Randall-Page, Matthew Spender and Emily Young, and newer talent such as Nick Turvey and the youngest here, Lucy Unwin, whose studio is nearby in the Cotswolds. There is a huge range of scale and style, and all are for sale.

Not all sculptures are outside. A good number, especially the smaller (more this year) are in the ballroom of this former Mitford family home. Others are in the office (where steak and chips awaits, courtesy of chef turned sculptor Julian Rena), the Cloisters, and inside the church where, amongst others, Guy Stevens’s The Maharajah’s Bone brilliantly offsets a painted wall.

From the moment you enter the grounds there’s a sense of excitement, fun, intrigue — and sheer quality — to this show. Off to the right, stands Lady Joan of Cornwall, four statues of her in fact, slightly different versions of the 14th-century effigy in Asthall’s church. In sculptor Matthew Spender’s hands the lady in a wimple has taken on a new lease of life in Tuscan Travertine. To the left is what may be the star of the show, it’s so well positioned. Paul Vanstone’s Close, two enormous profile heads carved in Carrara marble, surely has to be a conversation piece.

At the far end of the garden, having passed what seemed an inverted lightning bolt (Julian Rena’s Crack), a Magic Petal (Nicolas More-ton’s), a Pear built up of Westmorland Green Slate (Joe Smith’s), and Peter Brooke-Ball’s exquisite Tranquillity (Portuguese rosa marble, pewter and silver), leaving tamer for wilder parts, I followed a trail between lake and stream. Here, a line of upright sculp-tures includes Jonathan Loxley’s Nexus elegantly framing the fields (in sooth-ing grey Bardiglio marble), and Eirene by Aly Brown evoking the goddess of peace in Portland stone.

We respond to stone physically. There’s a natural impulse to touch, to enjoy a sculpture’s feel and form, take the experience beyond the eye.

One of the best things about on form is that visitors are encouraged to touch the sculptures. And who could resist works like Anthony Turner’s Eastern Peas or Dominic Welch’s Silent Moon II beautifully fashioned from deliciously smooth Kilkenny limestone?

Come rain or shine on form is a terrific experience.

It is open until July 15, there is a café this year, and events including workshops for adults and children, talks and theatre. See www.onformsculpture.co.uk