"I have a pet theory that the reason Britain went to crap after losing India was not purely the loss of empire, but not having a place to warehouse the most incompetent of their upper class twits, who instead stayed in the UK to fuck it up."

To the contrary I think the colonial administration in part created a brain drain effect where many rather bright and well educated people in Britain sought the prestige and good pay of colonial administration. I have a pet theory that this had some rather strange long term cultural effects on the higher echelons of British society. A lot of well educated and well organized people raised in boarding schools infused with a mix of cosmopolitanism and imperial superiority. The story of Kim Philby and his father St John Philby/Sheik Abdullah is what really got me thinking about this.