The UK government reported a record number of new coronavirus cases in Britain as a mutated strain of the disease increased infection rates. Britain reported 41,385 new Covid-19 cases on Monday and 357 deaths. It was the first time the UK has reported more than 40,000 new cases. The figures were worsened by the Christmas holiday weekend, with some reporting delayed until Monday. "This very high level of infection is of growing concern at a time when our hospitals are at their most vulnerable," said Yvonne Doyle, medical director at Public Health England. Hospitals are cancelling non-urgent procedures as beds are again filled with Covid-19 patients. UK Prime Minister Boris Johnson and his scientific advisers have said the coronavirus variant, which could be up to 70 per cent more transmissible, was spreading rapidly in Britain. But it is not thought to be more deadly or cause more serious illness. In mid-December when the mutation was first identified in the region, London and its surrounding areas were placed in Tier 4 restrictions. That includes non-essential shops closing, a ban on indoor socialising and restaurants offering takeaway food only. On December 26, Tier 4 was extended north and east to include Oxfordshire and Cambridgeshire, and now 24 million people in England are in the harsh lockdown. Mr Johnson said the spread of the new variant meant there would be difficult times ahead, and ministers said it might be necessary to go further. But on Monday, the government was still hoping schools could return to class next week. The rise in positive cases was partly driven by Northern Ireland reporting 1,634 new cases, having not reported any on Sunday or Friday because of the Christmas holiday period. Britain has increased testing capacity substantially since the first wave of Covid-19 in the spring. It has gone from about 100,000 daily tests at the end of May to 500,000 tests on December 23, the last day that data was published. British hospitals are struggling to find space for Covid-19 patients. Dr Nick Scriven, a former president of the Society for Acute Medicine, said on Monday that the rising number of patients in hospital was “extremely worrying". “With the numbers approaching the peaks from April, systems will again be stretched to the limit,” Dr Scriven said.