This has been coming a long time, over 15 years ago I read that the influx of doctors from the Indian sub continent in the 70's meant that many were coming up to retirement at roughly the same time.
My last GP in Ilford was a Sri Lankan chap in his late 70's, quality bloke that lived for his patients.
http://www.theguardian.com/society/2014/jun/14/gp-numbers-fall-recruitment-crisis-bites