The last Summer Olympics were held in 2012 in London.
The 2012 Olympics was held in London.
The Olympics were last held in London in 1948.
The date today is 12th October 2012 and the Olympics were held in London this summer, so 2012 is when they were last held in London. Before that they were held in London in 1948.
It has been held in the UK 3 times: 2012 (London) 1948 (London) 1908 (London)