Face masks will be handed out at Tube stations from Monday to help Londoners follow new rules demanding facial coverings on public transport.
Transport Secretary Grant Shapps announced that face masks will be mandatory on trains and buses from 15 June.
Masks should cover both the nose and mouth, and must be worn throughout a journey.
The new law will come into force the same day that high street shops, department stores and shopping centres begin to reopen in England.
TfL will start handing out single-use face coverings at busy stations from Monday (June 8) for the next few weeks.
The Mayor of London, Sadiq Khan, welcomed the new rules – he was already pushing for masks to be compulsory.
“I’m pleased that our lobbying has paid off and the Government has finally seen sense and made it mandatory for people to wear face coverings on public transport,” he said.
“This is something I and others have been calling on ministers to do for some time, and is in line with a large body of evidence that they can help stop the spread of coronavirus.”
Scientific advice suggests masks don’t stop the wearer from catching Covid-19 – but they can reduce the risk of those with the virus passing it on.
Anyone with coronavirus symptoms should self-isolate at home for seven days – but some people do not show signs when they have the disease, and could still risk spreading it to others.
The problem of public transport is particularly acute in London – almost half of residents don’t have a car, and rely on trains and buses to get around.
TfL is still urging everyone to avoid using its services unless they have no other option – and to walk and cycle where possible.
Public transport capacity in the capital has been slashed to just 15% of normal levels if social distancing is to be maintained.
TfL boss Mike Brown said passengers who need to use the network should “not wait” for the new law to come into force – and start wearing face masks now if they are not already.
“Face coverings can now be quite easily made or purchased, and we are helping by temporarily handing out free masks at hot spot Tube and bus stations,” he said.
“But the clear advice from the Government and Mayor remains – people should continue to work from home if they can and avoid travelling on public transport to create space for those who are making essential journeys.”