As I said earlier, economically, it might be better for London to separate from the Rest of the UK. London acts like a magnet, drawing all the economic activity towards it, and there is no counterbalance in the UK unlike other countries. Whitehall policies are also generally focused on the south and south-west, and these are enacted at the expense of the rest of the UK.
As such, if London leaves, it will no longer act like a magnet, thus it would give rise to growth and prosperity to other cities such as Manchester, Edinburgh, etc. Or we could have proper regional governments to help foster this.
Found an old article on the subject too...
http://www.bbc.co.uk/news/business-21934564
Bookmarks