Michelin-starred chef Raymond Blanc, together with Kate Humble, has been given the unique opportunity to spend a year at the most famous botanical gardens at Kew to re-establish the long-lost kitchen gardensthat once provided produce for the royal table from George II to Queen Victoria.It's spring at Kew and after a long, dark winter, nature is coming back to life. Raymond learns about the infamous rhubarb triangle before harvesting his own at Kew to make his sublime version of rhubarb and custard! What better to compliment this dessert than the exotic spice vanilla? Kate finds out how a 12-year-old slave enabled vanilla to become the world's most popular flavour.Nothing heralds the arrival of spring more than the first fresh asparagus, and Raymond plants some crowns at Kew. Domestic historian Ruth Goodman shows Kate an old Roman asparagus recipe and Raymond makes a light spring dish - grilled asparagus tips.For his fresh spring spinach and chorizo tortilla, Raymond harvests the first crop of potatoes of the season, while Kate discovers how war with France turned us into a nation of potato eaters. She also reveals how a toxic chemical was an ingredient used to brighten the colour of dull green canned peas in Victorian times.And as the season draws to a close, Kate takes a ride on the Watercress Line where she hears the rags-to-riches story of Eliza James, the Covent Garden 'watercress queen'. Back at Kew, Raymond and Kate sample some micro watercress to use as a garnish for Raymond's delicious pea risotto.