Hi, welcome to g o y, if it is fairly newly planted, did you keep it well watered during the heatwave in july?, if not it will have responded to not having enough water, by dropping its leaves, which the tree has now tried to replace since we started getting more rain, they will fall in autumn as normal, and will return next spring.
If I was you I would move the tree elsewhere, before it demolishes your fencing, they grow into pretty large trees and your fencing will not stop it, Derek.

Thanks :-)

Another 8 years and your horse chestnut could be 40ft high and spreading 15-20 ft across. It will need to be at least 40 ft from your house (and your neighbours') so that it doesn't crash through roofs/windows if it comes down in a storm. It may grow so that the branches are above the fence but, so that it isn't overhanging onto your neighbours' property, it will need to be 12-15 feet from any boundary - not really a tree for a domestic garden unless you have a spare half acre or so.

If you can get hold of a copy of the Kew Tree Root Survey you will get an idea of the space required. Also, you should be aware that a large tree in close proximity to your house may affect your building insurance, to the extent that you may actually nullify your insurance if you knowingly planted tree which later causes damage to your own or your neighbours' property.