Chinese President Xi Jinping (L) meets with British Prime Minister David Cameron at the latter's country retreat, Chequers, Britain, Oct. 22, 2015. (Xinhua/Ju Peng)

Chinese President Xi Jinping (R) and British Prime Minister David Cameron (2nd R) plant an oak tree symbolizing the China-Britain friendship in Cameron's country retreat, Chequers, Britain, Oct. 22, 2015.(Xinhua/Ju Peng)

Chinese President Xi Jinping (1st L) and British Prime Minister David Cameron (2nd L) talk with local people at a pub after their meeting in Cameron's country retreat, Chequers, Britain, Oct. 22, 2015.(Xinhua/Rao Aimin)

Chinese President Xi Jinping (3rd L) talks with British Prime Minister David Cameron (4th L) at a local pub after their meeting in Cameron's country retreat, Chequers, Britain, Oct. 22, 2015. (Xinhua/Ju Peng)

Chinese President Xi Jinping (L) meets with British Prime Minister David Cameron at the latter's country retreat, Chequers, Britain, Oct. 22, 2015.(Xinhua/Rao Aimin)

Chinese President Xi Jinping and British Prime Minister David Cameron take a walk at the latter's country retreat, Chequers, Britain, Oct. 22, 2015.(Xinhua/Ju Peng)