London (CNN)  -- A group of elderly Kenyans who say they were tortured under British colonial rule are seeking compensation at London's High Court in a case that could expose the UK to thousands of claims from across its former territories. Four Kenyans, aged in their 70s and 80s, have traveled from their homes in rural Kenya to press their claim that Britain is liable for the abuse they suffered during the Mau Mau uprising -- during which hundreds of ordinary Kenyans, including Barack Obama's grandfather, were arrested. Lawyers for the four say they suffered extreme acts of torture -- including castration and sexual assault -- at the hands of British administration officials in detainment camps during the uprising between 1952 and 1961.
@highlight
Four elderly Kenyans are seeking compensation for torture experienced during the Mau Mau uprising
@highlight
Case has exposed secret files covering Britain's rule of 47 colonies
@highlight
Mau Mau rebellion led to arrest of thousands of Kenyans including Barack Obama's grandfather
He says he survived a massacre at one @placeholder-run camp after which he lay unconscious for three days alongside 11 people who were killed.