CAMBRIDGE: Why does Indian Prime Minister Manmohan Singh so often opt for blue turbans? The secret was out Wednesday. It is the colour of Cambridge, his alma mater.

"My memories of my days in Cambridge are deep," the prime minister said in a speech after being conferred an honorary doctorate of law by the Duke of Edinburgh, Prince Philip. "The colour light blue is one of my favourites and is often seen on my head."

A university official explained later that blue was the colour of the institution.

Prince Philip also turned to the theme in his brief speech, saying amid some laughter: "You may note the colour of his turban."

Manmohan Singh, who became prime minister in 2004, studied economics as an undergraduate, gaining a first-class honours degree, the only first in his year in economics (1955-57).