British troops today begin their withdrawal from the Iraqi city of Basra. Six years after they helped in the US-led invasion to topple Saddam Hussein, some 4,000 British forces are starting a gradual pull-out.The process is expected to be completed by the end of July, although some 400 soldiers will stay on to continue training Iraqi forces. Britain sent some 45,000 troops to Iraq in 2003, and Basra was one of their main bases. On Sunday Iraqi officials held a farewell ceremony for the British forces. Britain is quitting Iraq to join the US in the fight against militants in Afghanistan. All American troops are due to leave Iraq by the end of 2011.