LONDON — Elusive British graffiti artist Banksy, whose identity is unknown, won the most entertaining documentary prize for his “Exit Through the Gift Shop” at the Grierson Trust British Documentary Awards in London on Tuesday evening.Film follows a French amateur filmmaker who tried to locate and befriend Banksy, who must retain his anonymity in order to continue his work, only to have the artist turn the camera back on its owner Lucy Bailey and Andrew Thompson won cinema doc prize for their “Mugabe and the White African,” about a family’s fight against Zimbabwe’s land reforms, while Adam Low’s “Arena: T.S. Eliot,” about the British poet, won for arts doc. The honor for historic doc went to Julien Temple’s “Requiem for Detroit,” a look at post-industrial Detroit and its burgeoning urban agricultural movement, while the drama crown was won by Peter Travis and Paula Milne for “Endgame,” dramatizing the final days of apartheid in South Africa. David Hickman won the science prize for his “Race and Intelligence: Science’s Last Taboo” examining IQ differences between different nationalities, and the international documentary award on a contemporary issue went to Mat Whitecross for “Moving to Mars,” charting two Burmese families as they relocate from a refugee camp on the Thai/Burma border to homes in the U.K. Andrew Lang won the Jonathan Gili award for newcomer for “Sons of Cuba” and a cash prize of £3,000 ($4,800) toward his next project. Patrick Forbes won for docu series for “The Force,” about the work of the police in Hampshire. Veteran documentarian and filmmaker Penny Woolcock received the Trustees’ award for achievement.