Alan Titchmarsh presents a stunning series that reveals the amazing secrets behind Britain's great gardens, examining how they continue to influence gardeners, including himself, today. In the first episode, Alan visits Hatfield House in Hertfordshire to look at the key design features of the gardens of this 17th-century stately home. This was a time when horticulture and architecture worked seamlessly together and Hatfield reflects this new love of the aesthetic. Alan examines the famous parterres which are some of the first examples of Britain's affection for formal gardening, and shows how the parterre has been brought into the 21st century by designer Tom Stuart-Smith with his designs at Broughton Grange in Oxfordshire. Alan also looks at the use of perspective, which at Hatfield makes the driveways seem bigger and changes how the garden is seen from different points of view. He look at a French import, espaliers, that have been used to stunning effect in Hatfield and show how these have changed the way we contort trees in our garden, including his own tip on stepover apple trees. Plus, he reveals how our affection for topiary began in gardens such as this where they were originally seen as architectural forms, complementing the design of the house. Alan shows in his own garden that you don't need to plant hedges to achieve this, creating a portable sedum cube.