BRITAIN asked Nigeria to explain where and how Nnamdi Kanu, a separatist leader who holds British citizenship, was arrested after Kanu's lawyer alleged he had been detained and mistreated in Kenya before being sent back to Nigeria. Kanu, leader of the Indigenous People of Biafra (IPOB) group which wants part of southeastern Nigeria to secede, was on the run outside Nigeria for four years until he was brought to court in Abuja on June 29 and told he would face trial. "We are seeking clarification from the Nigerian government about the circumstances of the arrest and detention of Nnamdi Kanu,"…