Well, DVD and books arrived. Tori and I watched the DVD this afternoon and it is every bit as good as Mossy says. Absolutely easy to understand, Gillian explains it all so simply and the way the painting of the horse illustrates the movement is fascinating. I couldnt recommend this more highly

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The book I have also been meaning to get for ages- and looks to be every bit as good. The Pilates exercises book is more or less covered in the main book, so I don't think I would have bought had I seen them both first.
But truly as good a DVD on biomechanics for the horseowner, as you would ever find.