I have a 2 metre by 3 metre plot which is really a huge container, with a
brick retaining wall and a concrete base under 2 feet of soil. I'd like to
grow a small tree there. Would a small apple tree cope with this (North-East
England, sunny, very near coast but well sheltered from winds), and if so,
what rootstock would you suggest (bigger than step-over or cordon
preferably) ? Or other kinds of fruit-tree ?

Thanks for any suggestions

Duncan