The most popular gardening event of the year comes to the National Exhibition Centre in Birmingham, where the Gardeners' World team celebrate 40 years of the programme with the building of the 40th year anniversary garden. Joe Swift aims to win a coveted RHS medal for the show garden, while Carol explores the RHS Floral Marquee, Rachel takes a look at the show gardens, Monty mans the seed swap and Michelle Robinson offers her take on the best gardening day out of the year.