Israel has refused to confirm or deny any involvement in the January killing of Mahmoud Mabhouh, a Hamas commander, in a Dubai hotel. br br But Dahi Khalfan Tamim, the emirate's police chief in charge of the investigation, is convinced Mossad, the Israeli spy agency, sent a squad to Dubai to assassinate Mabhouh.br br Al Jazeera's Dan Nolan has this exlcusive interview with the man fast-becoming a hero across the Arab world for holding Israel to account.