Days ago the Nigerian Government announced a ceasefire deal with the militant group Boko Haram - officials predicted the imminent release of more than 200 schoolgirls abducted by the extremists last April. Now those words look depressingly premature. What is going on with Nigeria's insurgency? Stephen Sackur speaks to Shehu Sani, a Nigerian human rights activist and sometime mediator with Boko Haram. How can the conflict which has cost thousands of Nigerian lives be ended?