A tree that size must be 15 years old..not even going to ask how much it cost!
It was a "bargain" price of £100 when it was on sale. Unfortunately that was the cheapest plant I bought that day because the mature olive tree I bought at the same time almost gave me heart palpitations when I had to make the payment
You have expensive taste 😃 good luck with them, it's stressful having unhappy mature specimens. Do let us know how it goes.
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https://www.urbanjungle.uk.com/aboutnorfolk.asp
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.