Alan Titchmarsh and Joe Swift take an exclusive peek around the Royal Horticultural Society's centennial Chelsea Flower Show before the gates open officially. Carol Klein shares her memories of exhibiting at the event and takes a look around the Great Pavilion. Nicki Chapman walks through the Generation Gardens to see how the country's front gardens have changed over the decades, while designer Chris Beardshaw explains how he gained inspiration from his experience of living with arthritis. And Laurence Llewellyn-Bowen explains why gnomes have been granted access for this year's show.