You don't see many overweight professional gardeners, not among the ones who do their own hard graft anyway, and having just spent several hours helping to create the new rose garden at Kew Gardens, I know why. Marking out, cutting and rolling turf, wheelbarrowing the rolls and offcuts to the skips, edging the new beds and using a lifting iron to remove the surplus uses up hundreds of calories. My body was begging for a reprieve after four hours; in fact I was secretly relieved to be able to peel off and head for my day job.