Countryfile: Northants

Anita Rani's in the Nene Valley, where a pioneering project is just about to launch. Retail giants have been working with the Wildlife Trust to create a shopping destination where wildlife and retail come face to face. For centuries Northampton has had a thriving leather industry, John Craven meets two local lads who have set up a micro-tannery to tan goat hides. John then goes on a butterfly hunt to try to catch the purple emperor. Considered the 'holy grail of lepidoptery', the beauty of this elusive creature belies its truly filthy nature 'his imperial majesty' doesn't feed on flowers, but rotten fruit, mouldy cheese, dog poo and anything that smells foul.