Love that link and I remember talking about this last year!
I have two trees growing from some chestnuts I gathered and tossed in the ground a few years ago that will have to be transplanted should anyone want to start their own conker tree.
One is probably 6-8 feet and have had to cut it back a few times already. The other I transplanted 2 years ago to a pot but I think it probably will have to be dug out of the ground beneath.