By Sruthi Shankar and Bansari Mayur Kamdar (Reuters) – European stocks tumbled to their lowest levels in 16 months on Thursday after policy tightening in Britain and Switzerland fuelled fresh worries about the impact of inflation on the global economy. Already under pressure at the open after the U.S. Federal Reserve’s big interest rate hike on Wednesday, the benchmark STOXX 600 fell further after the SNB’s unexpected rate hike. The index declined 2.5%, hitting its lowest level since February 2021. “There is very little to be cheerful about,” said Giuseppe Sersale, strategist at Anthilia in Mi…