Liverpool's Champions League clash against Atletico Madrid 'caused increased suffering and death' amid the coronavirus pandemic, a study has found.
The UK's largest Covid-19 tracking project pointed to the Anfield match plus the Cheltenham Festival as events that had accelerated the spread of the virus.
Many other countries suspended sporting events before the UK, despite the impending threat of coronavirus.
A full programme of football in both England and Scotland was held on the first weekend of March, as well as five horse racing meetings and England vs Wales in the Six Nations at Twickenham - attended by the Prime Minister.
Cheltenham opened its doors to 250,000 spectators on March 10, just 24 hours after Culture Secretary Oliver Dowden had rebuffed calls for a ban on mass outdoor gatherings.
"There's no reason for people not to attend such events or to cancel them at this stage," he said.
But Professor Spector from King's College London, leading the study, said people 'will have died prematurely' due to the decision.
"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," he added.
The BBC report figures show that - in the last week of March - Liverpool and Cheltenham were among the areas with highest number of suspected coronavirus cases.
According to the Covid-19 Symptom Study, an estimated 5-6% of the population in those areas, aged between 20 and 69, had symptoms.
The research was gathered from information uploaded by more than three million volunteers around the UK submitting daily reports on whether they had any of the 15 symptoms related to coronavirus.
Liverpool vs Atletico took place on the same day as the World Health Organisation declared the pandemic
Around 3,000 fans travelled from Madrid, despite the Spanish capital being considered an epicentre for the outbreak of coronavirus in Spain.
Liverpool fans Joel Rookwood has been ill in the aftermath of the match, and thinks he contracted coronavirus on that evening.
"The celebrations were some of the most physical that I've experienced," he said. "People were jumping all over each other."
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."