Britain has a stockpile of 240,000 doses of dexamethasone, the steroid that has been shown to reduce the fatality rate of those suffering in the later stages of coronavirus, Health Secretary Matt Hancock said on Wednesday.
Hancock told the UK parliament that the trial by Oxford University of the drug was "an important moment in the fight against this virus."
"It is the first time the world that anyone has proved that a drug can improve the survival chances of someone suffering from coronavirus," he said.
Hancock added that the UK currently had 240,000 doses of the drug stockpiled and that treatment with it would begin immediately on the NHS.
"It is not a cure, but it is the best news we've had... This is what good science looks like," he said.
Meanwhile, British Prime Minister Boris Johnson called on his colleagues in parliament to get behind the re-opening of schools in the UK as the country's coronavirus lockdown winds down.
The government's decision to re-open schools from June 15 has been controversial with both parents and opposition figures, who argue that it is too early.
Britain is currently the third-worst affected country globally, with more than 42,000 deaths and almost 300,000 cases.
Also in Prime Ministers Question Time, Labour leader Keir Starmer challenged the prime minister on childhood poverty, stating that a new report showed an anticipated rise in childhood poverty.