LONDON: Downing Street had an unusual visitor on Thursday: a 10-year-old boy whose father has been languishing in the U.S. detention centre at Guantanamo Bay for nearly four years on what his family claims are trumped-up charges. Anas el-Banna, accompanied by his younger brother Mohamed, delivered a letter addressed to Prime Minister Tony Blair urging him to intervene to get his father, Jamil el-Banna, back home. "Why is my dad far away in that place called Guantanamo Bay? Why can't my dad come home'' he asked as a large protest rally was held outside the U.S. embassy demanding the closure of the camp. Anas said he was "disappointed'' that Mr Blair had not replied to his previous letters. His father, who has been held in Guantanamo Bay since March 2003, was picked up by American security forces in Gambia where he had gone to set up a peanut processing plant. His family says he suffers from severe diabetes but has been denied medication. Britain has refused to intervene on grounds that Mr El-Banna, a British resident of Jordanian origin, is not a British citizen, although his wife and children hold British passports.