Secrets of the National Trust - Season 4

The presenter returns to visit a house in West Sussex known as `the house of art". Sat in beautiful Capability Brown-designed grounds, Petworth House was home to the third Earl of Egremont, whose passion for British art saw the abode become an art school for the nation's talents. Plus, Jennie Bond discovers a Grand Tour with a difference, and Peter Purves navigates the Chichester Canal to reveal it wasn't just the art world which benefitted from the Earl's investment.

The presenter explores Chartwell, the Kent country house that was once Winston Churchill's family home. He is allowed exclusive access to the wartime prime minister's documents - and helps to restore his bricklaying handiwork. Miriam O'Reilly visits Coleshill Estate near Swindon, where a secret auxiliary army was trained to defend Britain in the event of an invasion.

Alan explores the lives of Plas Newydd's former residents - from the brave 1st Marquess of Anglesey who fought in the Battle of Waterloo to his wild descendant who nearly bankrupted the family. Later Alan learns of the unrequited love between the great British artist Whistler and the daughter of the 6th Marquess.