LONDON (Reuters) - Britain tightened COVID-19 restrictions in three more areas of England on Thursday, putting them in the “high” category of the UK’s three-tier system, meaning people will not be able to mix outside their households. “We’re seeing rising rates of infection in Stoke-on-Trent, in Coventry and in Slough. In all of these areas, there are over 100 positive cases per 100,000 people, cases are doubling around every fortnight and we’re seeing a concerning increase of cases among the over-60s,” health minister Matt Hancock told parliament. Several cities in northern England are in the top “very high” category, which requires the closure of hospitality.