The last few weeks have seen companies rushing to update the market with news of how Covid-19 has affected their businesses. In many instances the impact has been seismic: trading has slumped or ground to a halt entirely, and earnings guidance has been largely withdrawn. And as cash flows have dried up, many companies are facing a grim battle for survival that has meant deep cost-cutting, cancelled investment programmes, and a swathe of dividends cuts and emergency fundraisings.