By Sruthi Shankar and Bansari Mayur Kamdar (Reuters) -Britain’s main stock indexes fell on Tuesday, as geopolitical risks and the prospect of higher interest rates hit global markets, with investors focussing on fresh measures by the Bank of England (BoE) to try to stem the rout in government bonds. The central bank, battling to stabilise Britain’s 2.1 trillion pound ($2.3 trillion) bond market, said it would buy up to 5 billion pounds of inflation-linked debt per day, starting Tuesday, until the end of this week. The pound reversed course and gained 0.8%, weighing on the export-heavy FTSE 100…