Britain's biggest companies adopted their most defensive stance since early 2020 in the run-up U.S. President Donald Trump's April 2 tariff announcements and focused on boosting cashflow, cutting costs and reducing borrowing, a survey showed on Monday. Deloitte's quarterly survey of chief financial officers at major British firms, conducted March 18-31, found their optimism about their firms' financial prospects was still higher than after Russia's full-scale invasion of Ukraine and the start of the COVID-19 pandemic.