Covid-19 torments two types of company: the ones that deal with crowds of people, and the ones with a lot of debt. Mitchell’s & Butler’s, the British pub chain 23.5 per cent owned by JP McManus and John Magnier, is both.  Mitchell’s & Butler’s is the second-biggest listed UK pub and restaurant chain. It runs 1,748 pubs across the UK. If you’ve ever been on a night out in a British town, chances are you’ll have passed one of its brands — an O’Neill’s, All Bar One, Toby Carvery or Harvester.  As recently as March, Mitchell’s & Butler’s was in…