Overview: Alan Titchmarsh and Joe Swift take a first peek at the Royal Horticultural Society's Chelsea Flower Show 2011 in this exclusive preview of the event. With show opening only hours away, they are joined by Andy Sturgeon, Nicki Chapman and Christine Walkden to see what horticulture's finest are exhibiting this year. Plus they reveal the behind-the-scenes preparation that designers, landscapers and nursery folk do in order to exhibit at the most prestigious event in the gardening calendar.