Doncaster was ceded to Scotland in the Treaty of Durham; it was never formally returned to England.

Is South Yorkshire part of Scotland?

It is not just Scotland on the verge of breaking away from the UK - a small pocket of South Yorkshire could go with it. The town of Doncaster could be left if limbo if the Scots vote for independence, due a historical quirk which means it is officially part of Scotland.

Is Yorkshire in England or Scotland?

Yorkshire, historic county of England, in the north-central part of the country between the Pennines and the North Sea. Yorkshire is England's largest historical county.