What is the difference between hack pony and a Galloway?

The Galloway is a now extinct pony of the mountain type. They were absorbed into the Fell and Dales pony breeds and looked very similar to both. As for the Hack pony, there are two versions of this, a true hack pony and 'Hack' as in a shortened form of Hackney pony, which are two different things. A hack pony is like a smaller version of a hack horse which is a type of lightweight riding/show horse used in the UK. They are supposed to be very well mannered and a smooth ride. A Hackney pony on the other hand was primarily developed as a light carriage/harness pony with highly elevated and flashy movements.