LONDON (Reuters) - Britain said on Tuesday it had summoned the Chinese ambassador in recent days to express its concern that a British rights activist was denied entry to Hong Kong last week.  We are very concerned that Ben Rogers, a UK national, was denied entry into Hong Kong on 11 October in absolute disregard of the  one country, two systems  principle,  Foreign Office minister Mark Field said in parliament. He added:  Foreign Office director-general for economic and global issues summoned the Chinese ambassador on this issue over the past few days.  Rogers, a co-founder of the ruling Conservative Party s Human Rights Commission, has been a vocal critic of Chinese-ruled Hong Kong s treatment of human rights activists, including that of jailed student protest leader Joshua Wong. Hong Kong, which returned to Chinese rule in 1997, is governed under a  one country, two systems  principle that promises it a higher degree of autonomy and freedom than on the mainland. Last week, Foreign Secretary Boris Johnson said London needed an explanation from Hong Kong and Beijing on the matter. 