Help!!! Vinca major?

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We have a very good Vinca, which are going to propagate but we don’t know what it is. It is probably a form of V. major but the flower is more violet than blue, it only grows to about 20cm and the leaves are smaller than most forms of Vinca major. It is not V.m ‘Oxyloba’ (syn ‘Dartington Star’) because the leaves petals are too broad and not pointed; and I don’t think it is ‘Jason Hill’ which I don’t know, but which is supposed to have broad but pointed petals which ours has not. Can anyone help? nick@jackdawsfield.co.uk