In article , Jim Lewis
wrote:

Cast-it Admin wrote:
I know nothing about bonsai or even basic pruning techniques of trees.

My son planted a conker 12 years ago in an old flower pot. Aft a few
transplants it is now 6ft tall and is an ideal size for new little patch of
England - can I use bonsai techniques to keep it at that kind of height and
still maintain an attractive looking tree?

If so, can someone give me some hints please

The key "bonsai technique" is keeping the roots tightly
constrained and in a pot, so if this is planted in a "new little
patch of England" that technique would be not available to you.

However, you always can prune a tree down to some pleasing size.
I don't think horsechestnuts are very large trees, anyway, are
they?

It depends. According to Wikipedia there are 20-25 species, which can grow
to 4-35m tall depending on the species.

The Common Horsechestnut (Aesculus hippocastanum) is widely cultivated, and
British children play a game with its seed or "conker", so that may be what
he has. It can grow to 35m.