“Compared with the epic works that have made his name – the shark in formaldehyde, the bisected cow – Damien Hirst’s work in progress is a small, delicate object: a life-size human skull. Not just any skull, mind, but one cast in platinum and encased entirely in diamonds – some 8,500 in all. It will be the most expensive work of art ever created, costing between £8m and £10m.”