England, Scotland, and Wales formed a customs union after 1707 and this included Ireland after 1807. So the national market was not hindered by internal customs barriers.

• 1707年后,英格兰、苏格兰和威尔士形成关税联盟,1807年后爱尔兰加入。因此,全国市场不再受阴于内部的关税障碍。