The UK's largest coronavirus tracking project has said that Liverpool's controversial match with Atletico Madrid in March 'caused increased suffering and death.'
Data gathered from millions of volunteers found coronavirus 'hotspots' shortly after the March 11 Anfield clash as well as after the Cheltenham Festival around the same time.
Professor Tim Spector of King's College London said rates of cases locally 'increased several-fold' after the two events.
The Liverpool Echo and others have been regularly questioning the decision to go ahead with the Liverpool-Atletico Champions League match.
The game saw 3,000 fans travel to Liverpool from the Spanish capital, where there was an acute outbreak of Covid-19 and strict lockdown measures.
The Madrid fans were unable to watch their own team play at home at that time, but were able to fly to Liverpool, socialise in the city and attend a sell-out Anfield.
At the time government advice was that events like the Madrid match and Cheltenham could go ahead as they would not have a big impact on transmission.
Sports governing bodies in the UK were taking their cue from Prime Minister Boris Johnson who declared in early March that people should "as far as possible, go about business as usual".
Just 24 hours before Cheltenham opened its gates to 250,000 spectators on March 10, Culture Secretary Oliver Dowden rebuffed growing calls for a ban on mass outdoor gatherings.
He told the BBC: "There's no reason for people not to attend such events or to cancel them at this stage."
And the next day, ahead of kick off between Liverpool and Atletico, deputy chief medical officer Jenny Harries told Boris Johnson in a twitter Q and A that such events would not have a big impact on spreading the virus.
But Professor Spector said "people will have probably died prematurely" because of the decision to go ahead with these events.
Figures seen by the BBC Radio 4's File on 4 programme show in the last week of March, Liverpool and Cheltenham were among the areas with the highest number of suspected cases.
The figures come from the Covid-19 Symptom Study, and show an estimated 5-6% of the population, aged 20 to 69, having symptoms in those two regions.
The research draws on information uploaded by more than three million volunteers around the UK, who submit daily reports identifying whether they have any of the 15 symptoms associated with the virus.
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Prof Spector said: "I think sporting events should have been shut down at least a week earlier because they'll have caused increased suffering and death that wouldn't otherwise have occurred."
In a statement, the government said: "There are many factors that could influence the number of cases in a particular area, including population density, age, general health, and the position of an area on the pandemic curve."
Separate modelling from Edge Health, which analyses health data for the NHS, found that the Liverpool-Atletico match could be linked to 41 extra deaths at local hospitals in our region between 25 and 35 days after the game.