Why do some runners run under England and other runners under the United Kingdom flag?
I can't answer for everyone but if you are English you are also British. Some of us feel more allegiance to England, others to GBR (strictly speaking the United Kingdom of Great Britain and Northern Ireland ).
I happen to be the England Manager for the Home International team. Therefore it seems appropriate to run as England rather than GBR.
It is complicated here.
I'm presently watching 'England 'play cricket against Ireland. The England team actually represents England and Wales. I think the Ireland team represents the whole island of Ireland.
LOL, now everything is clear, or not? ;-)
Sometimes things are complicated by organisers using a Union flag for England or competitors wearing GB kit when representing England...
Strange thing is Scots never wear GB team when running for Scotland...
The worst thing is that the English use the GBR National Anthem. About time we adopted Jerusalem.
I select ENG when entering home events, GBR when abroad. Of course, I'm not running for either of them.