Kew Gardens is famous round the world. Its magnificent palm house is an unsurpassed marvel of glass and cast iron architecture, home to tender trees from un-British climates such as Brazil and Madagascar. Its pagoda is more than 130ft high, the tallest and arguably the earliest tribute to Chinese gardens in Europe. Its herbarium of dried and pressed plants is an international wonder, spanning centuries of collected material, which has now jumped into unexpected life, thanks to our new understanding of genetics where DNA can be recovered from dried leaves and flowers even when the original plant has become extinct in nature.