Zimbabwe's opposition leader, Morgan Tsvangirai, said last night that he had been involved in secret talks on a power-sharing government with senior figures from Robert Mugabe's regime. Mr Tsvangirai said a mediator had offered a deal under which Mr Mugabe, who was re-elected last year in elections widely condemned as rigged, would resign and be given immunity from prosecution. Senior Western diplomats said that the offer appeared to be a trap to co-opt the opposition. Mr Tsvangirai said the offer was made, via the intermediary, by two of the ruling party's most powerful figures - the speaker of the Parliament,...