One Planet - Cities for people, old trees and missing billions

Cities are being built to make cars happy, not to allow society to flourish. That's the argument made by Danish architect Jan Gehl. Mike meets up with him to walk through one of London's most famous squares and hear how town planners are failing the people they are supposed to be helping. Dr Gehl, who's advised cities around the world from London to New York, pleads for an end to the world's obsession with tarmac.

Also in the show we consider the case of $40bn of missing money. That's the amount of cash being lost from developing countries every year through corruption and bribery according to the World Bank. The organisation has now issued a handbook designed to help governments get back the stolen money. We speak to the World Bank, plus we hear a successful example from Peru of how to recover corrupt cash.

And then there's the artist who's travelled the world seeking to photograph the oldest living organism. Our reporter Matt Wells in New York meets with Rachel Sussman, and asks her to find the oldest thing in her home town - it's a tree apparently. See photos from this week's programme on our Flickr album. Plus don't forget to join us on our Facebook page to see exclusive slideshows and videos.