Monty Don, Joe Swift and Rachel de Thame are joined by Carol Klein and Toby Buckland at this year's RHS Hampton Court Palace Flower Show. Monty discovers the vital but invisible creatures that lurk within our gardens. Joe learns about the plight of Britain's hedgehogs and discovers how gardeners can help. Carol looks at plants that attract pollinators to your garden, whilst Toby is solving everyday garden design problems. Rachel enjoys this year's brand new roses and Matthew Keightley, winner of The People's Choice award at this year's Chelsea Flower Show, takes a look at this year's must have plants.