It is not likely that anyone has restored and maintained as many gardens as has Graham Stuart Thomas. And what gardens they are: at the castles, such as Powis, Scotney, and Sizergh; the parks, such as Sheffield, Tatton, and Stourhead; and at much-visited gems such as Hidcote Manor, Sissinghurst, and Snowshill. These are a few of the hundred or so garden properties in care of the National Trust for which he was responsible during 18 years as its horticultural...