 In the early 1960s he was a legal adviser at the Lancaster House conferences in London where Kenyatta and the Kenyans worked with the UK Colonial Secretary, Reginald Maudling, and his team to develop a constitution for the country.In 2001 de Souza told the Constitution of Kenya Review Commission why he felt the Lancaster House Constitution had been a good constitutional framework, and expressed his disagreement with some subsequent changes, especially the re-introduction of detention without trial.The Ministry of Overseas Indian Affairs has described him as making "a principled exit from public life in the 70s".