Britain's prime minister Boris Johnson will return to work at the start of this week, according to reports Sunday just hours after it was announced that the UK's coronavirus death toll had passed the "tragic" milestone of 20 000.The Press Association said Johnson would be back in his Downing Street office on Monday after himself recovering from the virus.A Number 10 source quoted by Sky News said the 55-year-old was "raring to go". Johnson has been recuperating at the British prime ministerial retreat, Chequers, outside London since his release from hospital on April 12Johnson spent three days in intensive care and later admitted "things could have gone either way", after contracting the virus.The prime minister's return to work comes as pressure intensifies on his government on several fronts over its handling of the crisis.Health department figures released Saturday showed a further 813 people had died in hospital after contracting Covid-19, pushing the official number of fatalities to 20 319.Home Secretary Priti Patel described it as "a deeply tragic and moving moment".Passing 20,000 was an unwanted milestone, as the medical director of NHS England Stephen Powis and Britain's chief scientific advisor Patrick Vallance had said previously during the pandemic that keeping the number of fatalities below 20 000 would be "a good outcome"."The nation today will be deeply moved by the figures of the number of people who have died," Patel said during the daily Downing Street briefing. It was an increase on the 684 deaths reported the previous day and comes after the government claimed the virus had hit its peak.However, there was some optimism as the number of new infections fell by 473 to 4 913, according to the same health department figures.University of Oxford analysis also showed that the numbers dying in England may be on a downward spiral as it said a third of the 711 additional deaths recorded in the latest government figures on Saturday occurred more than a week ago.Despite that, the latest figures confirm Britain has been one of the worst-hit countries in the world and the actual death toll could be much higher when deaths in the community are taken into account, particularly at care homes.As well as a rise in fatalities, questions are being asked of the government over shortages in personal protective equipment and a lack of widespread testing, particularly of frontline health and social care workers.There is also pressure, reportedly from within the ruling Conservative party, to relax social distancing rules.Johnson ordered the country into lockdown on March 23, but Patel said ministers would not yet give a date for any relaxation of the rules."We've made a great deal of progress, but actually we're not out of the woods yet, we really are not," she said. The lockdown was extended on April 16 and is due for review on May 7.Concern over political influenceMeanwhile there was brewing row over the role played by Johnson's controversial chief advisor, Dominic Cummings, after it emerged he attended meetings of the main scientific group advising ministers on the coronavirus pandemic.Downing Street denied that Cummings and another advisor, Ben Warner, were members of the politically independent Scientific Advisory Group for Emergencies (SAGE).However, following reports in The Guardian newspaper, the government admitted that Cummings had sat in on group meetings.In a statement, a Number 10 spokesman said they attended meetings "to understand better the scientific debates concerning this emergency".The statement added it was "factually wrong and damaging to sensible public debate" to suggest the committee's advice was affected by the government.Labour's health spokesman, John Ashworth told BBC radio on Saturday that his "concern" was "that political advisers have influenced the debate".And a former Conservative frontbencher, David Davis, tweeted that "we should publish the membership of SAGE: remove any non-scientist members".Meanwhile on Saturday, health officials announced that as many as 5 000 severely ill coronavirus patients could be treated with plasma from people who have recovered from the illness as part of a new approach.