Posted: 28/06/2015 at 15:12
"My Secret Garden" by Alan Titchmarsh and was published in 2012.
Not sure that helps but I'm sure the answer will be in there.
Edit: It's formally clipped yew and box, apparently.
I have a copy (a GW Advent Calender 'prize') from a couple of years ago.
On page 102 Alan writes about his "lollipop yews" planted in "... Italian Terrace Pots, 'Vaso Archi' 80cm in height and diameter with a Gothic arch pattern to their rim. They age beautifullyu, taking on a duisky patina to the terracotta, which is not as vivid an orange as its British counterpart. They have also withstood freezing temperatures in at least two severe winters..."
Hope that helps