On 8 January 1972 the leader of the Liberation War and Liberation movement Sheikh Mujibur Rahman was released from Pakistan Jail and was sent to London. On Mujib's arrival in London, he was met by the Prime Minister of UK and other world leaders. Sheikh Mujib returned to Bangladesh on 10 January 1972, by a British Royal Air Force Aircraft. Mujib congratulated the Bengali Mukti Bahini (the Bangladesh Liberation Force) for succeeding in the war of liberation against Pakistan army. Mujib was placed at the helm of government, according to the election victory under the unified Pakistan government. In 1973 after the first Bangladesh elections, he continued his term in office with immense backing from India, and public popularity, but had great difficulty transforming this popular support into the political strength needed to function as head of government. The new constitution, which came into force on 16 December 1972, created a strong executive prime minister, a largely ceremonial presidency, an independent judiciary, and a unicameral legislature on a modified Westminster model. The 1972 constitution adopted as state policy the Awami League's (AL) four basic principles of nationalism, secularism, socialism, and democracy. A key author of the constitution of Bangladesh was Dr Kamal Hossain, who has since been a major political figure of the country.