Government policies on discharging untested patients from hospital to care homes in England at the start of the Covid pandemic have been ruled unlawful by the High Court.
The ruling comes after two women took the former Health Secretary Matt Hancock and Public Health England to court.
Dr Cathy Gardner and Fay Harris said it had caused a "shocking death toll".
The government had said it "worked tirelessly" to protect the public.
Dr Gardner and Ms Harris partially succeeded in claims against Mr Hancock and Public Health England.
In their judgement, Lord Justice Bean and Mr Justice Garnham found the decisions of the health secretary to make and maintain a series of policies contained in documents (issued on 17 and 19 March and 2 April 2020) to be unlawful. Both Justice's asserted that the drafters of these documents failed to take into account the risk to elderly and vulnerable residents from non-symptomatic transmission.
The judgement would go on to state that: "Non-symptomatic transmission would mean that one elderly patient moved from hospital to a care home could infect other residents before manifesting symptoms, or even without ever manifesting symptoms. The judges found that it was irrational for the DHSC not to have advised until mid-April 2020 that where an asymptomatic patient (other than one who had tested negative for COVID19) was admitted to a care home, he or she should, so far as practicable, be kept apart from other residents for 14 days."
Dr Gardner's father Michael Gibson was 88 when he died on 3 April 2020 while living in a home in Oxfordshire during the UK's first lockdown.
His cause of death was given as "suspected Covid" after the home took in a patient discharged from a hospital with the virus.
A spokesman for Matt Hancock said the case "comprehensively clears ministers of any wrongdoing and finds Mr Hancock acted reasonably on all counts".
"The court also found that Public Health England failed to tell ministers what they knew about asymptomatic transmission," she said.
"Mr Hancock has frequently stated how he wished this had been brought to his attention earlier."
During Prime Minister's Questions in the House of Commons, Prime Minister Boris Johnson said: "Of course I want to renew my apologies and sympathies for all those who lost loved ones during the pandemic, people who lost loved ones in care homes."