How and when did the British surrendered.

 
The British & Commonwealth forces surrendered at Singapore largely because of the swiftness & surprise in the attacks by the Japanese in the Malay peninsula. Hugely stretched by the potential war in Europe & the actual war against the Axis in North Africa the British lacked the resources to defend the Far East against Japanese aggression. With hindsight it might be argued that surrender was premature, but even then defeat was surely inevitable in the longer term. Had the Japanese attacks not involved the US, bringing them into both the Pacific & European conflicts, then Britain & the Commonwealth are under the sort of pressure which may have become intolerable.

The Japanese actually tricked Singapore by lying that a huge troop of Japanese would come and attack Singapore the next day if the British did not surrender. However, the Japanese actually did not have that big troop of army and their supply of necessities were depleting. If the British did not surrender, the losing side might be the Japanese instead. http://wiki.answers.com/Q/Why_did_the_british_surrender_in_Singapore