We have an annual picnic in the private gardens of Kensington Park Gardens, the grandest boulevard in west London (well, we’ve done it two years running which makes it feel like a tradition).   I’m always amazed by the scale and the spaciousness of these private gardens, a product of mid-nineteenth century bourgeois opulence, with nannies using them to park prams and businessmen can have their morning constitutional.   They occupy the site of a racecourse known as the Hippodrome owned by the Ladbroke estate.   Hence Ladbroke Square.   Nine acres, the largest private gardens in London after Buckingham Palace.   We had supper in a glade with monogrammed white table napkins and the sound of tennis in the background.