In this first episode, it is spring at Kew, and after a long, dark winter, nature is coming back to life. Raymond learns about the famous rhubarb triangle in Yorkshire, where early rhubarb was produced, before harvesting his own at Kew to make his sublime version of rhubarb and custard. And what better way to complement this dessert than with the exotic spice vanilla? Kate finds out how a 12 year-old slave enabled vanilla to become the popular flavour it is today.