Len Castle trained as a secondary schoolteacher and started making pottery in 1947. Initially self-taught, he was the first potter to be awarded a fellowship from the Association of New Zealand Art Societies, travelling to St Ives to work with Bernard Leach in 1956-57.
In 1963 Len gave up lecturing science at Auckland Teachers' College to become a full-time potter. He was a founding member of the New Zealand Society of Potters in 1963 and has been a regular exhibitor in the annual New Zealand Studio Potters exhibitions, which started in 1967.
An essential part of Len's career was his overseas exposure. In 1966-67 he studied in Japan and visited potters in Korea and China, returning there in 1974 as a member of a cultural delegation sponsored by the New Zealand Department of Foreign Affairs, when he also visited potters in Korea and China. He returned to influence a generation of potters. In 1991 he was one of twelve New Zealand ceramicists invited to represent New Zealand at the World Expo in Seville, Spain.
With his scientific background, Len was always curious about the natural world and was interested in extending his knowledge and understanding of it. He enjoyed constant exploration, an attitude that opened the paths of creative production for him. He usually started with a distinct idea for what he wanted to achieve in a new project and after 62 years of potting experience was extremely adept at translating this idea into the finished product. Of course the results did not always match the artistic vision that inspired them, but after a lifetime dedicated to potting; they were generally pleasing, as he modestly acknowledged: "I'm at my peak. I used to say, I can't often hit the nail on the head; now I can say I hit the nail on the head more often."
Len received a CBE for Services to Pottery in 1986, a New Zealand Commemorative Medal in 1990. He received an Arts Foundation of New Zealand Icon Award in 2003, and a Distinguished Alumni Award from the University of Auckland in 2004. In 2004 he was also awarded a D.C.N.Z.M (Distinguished Companion of the New Zealand Order of Merit) for Services to Pottery
Len travelled extensively, demonstrated and judged at exhibitions, while producing his works.
Mountain to the Sea, a touring exhibition containing approximately sixty works, organised and curated by Tanya Wilkinson with the support from the Hawke's Bay Museum & Art Gallery and Creative New Zealand, toured to selected galleries around New Zealand thoughout 2009 and into 2010.
Len died at the age of 86 in 2011.