Sarah Dunant says the rediscovery of ideas from the past can help with 'the toxicity of the present'. Just as the Renaissance master Donatello drew from the classical world to create revolutionary art, so we can find a moment in history to inspire progress in our time.

'On the surface it seems like an impossible task' says Sarah, 'not least because like everything else in this angry, polarised moment, the past itself has been commandeered as a weapon...but the wonderful thing about ideas, is that while they can travel weightlessly through history, they still pack a punch.'

Producer: Sheila Cook Sound engineer: Peter Bosher Production Co-ordinator: Helena Warwick Cross Editor: Richard Fenton-Smith