Britons’ retirement plans at risk under a potential tax raid on pension pots, according to the head of one of the country’s biggest insurance companies. Aviva boss Dame Amanda Blanc is urging ChancellorRachel Reeves to not introduce a cut to pension tax relief in her upcoming Autumn Budget. This proposal is reportedly being considered as the Treasury looks for ways to fill the £22billion “black hole” in the public finances left by the last Government. One of the measures under consideration is a flat rate of tax relief at 30p in the pound. If introduced, higher-rate taxpayers would be slapped …