By Jack Barnett A new Covid-19 variant that escapes vaccines is among the biggest risks threatening to sharpen the UK recession, City economists surveyed by City A.M. suspect. Asked what wildcard trends could spring up to hit the economy this year, experts warned another deadly strain of the virus spreading was one of the biggest headwinds that would magnify Britain’s downturn. “In an extreme case some renewed lockdowns may be needed,” Sandra Horsfield, economist at fund manager Investec, said, although she highlighted vaccines could be tweaked quickly to minimise disruption. Paul Dales, chief…