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But your Campanula is definitely not C. carpatica Blue Clips. It looks more like a C. portenschlagiana,but to be sure a close-up of the leaf and a few flowers would be helpful.
and said the garden manager was very knowledgeable regarding plants
I'm glad you like it John.The Batsford tree is claimed to be the biggest/oldest example in the UK.The RHS Dictionary says it should 'flower' after 10 years.