Every year in Britain we drop 30 million tonnes of litter. Then we spend one billion pounds a year cleaning it up. It's crazy. And Margaret Mountford is sick of wading through other people's rubbish. So she sets out to discover what it would take to keep our country clean. Along the way she uncovers some surprising and shocking truths about litterers and their anti-social behaviour. Today, she stages an experiment to make train passengers stop dropping litter - by making the carriage smell of lemons. Sounds bonkers, but Dutch psychologists say it works, so Margaret tries it out on the Birmingham to Lichfield line. The results are surprising. A mind-boggling 24 tonnes of litter is dropped on Brighton Beach every summer weekend. The true story of one of our most iconic beaches is revealed by the cleaning teams who start at 5 am when the clubbers head home and face not only broken glass, needles, burning coals and human excreta, but violent abuse from the litterers themselves. It's a miracle that the beach is ever clean and safe enough for sunbathers. There are concerns about the plastic litter found in both the sea and the fish that live in it. Plymouth University's Prof Richard Thompson is researching micro plastic, tiny fragments produced when plastic litter is broken up by the waves. Thompson examines fish from a Devon market to discover how much plastic lurks in the fish we eat. In Edinburgh, wardens Brenda and Alex catch people who dump the entire contents of apartments on the streets. And, also in the Scottish capital, there's a group of volunteers who pick up other people's litter.