VH-EPQ was cleared into the Richmond Control Zone on track to Riverstone, not above 500 feet on QNH. VH-EPQ was observed by the control tower supervisor proceeding north of Riverstone. When challenged by the tower controller, he reported 2 nautical miles (nm) south of Oakville. VH-EPQ proceeded to Oakville from Riverstone without a clearance, breaking down separation with Stal Thunder One on Tacan One final. No Holding instructions were given to VH-EPQ by the tower. The pilot of VH-EPQ was contacted and he said that he had complied with the terms of his clearance and that at no time was he anywhere near the C130 which he saw about 2000 feet above and one and a half to two miles away.