Wearing a face covering in London is only currently mandatory on public transport but also advisable in places where social distancing is more difficult, for example in shops.
The evidence on the use of face coverings is limited, but there may be some benefit in wearing a face covering to prevent the spread of the virus from yourself to others. But please remember, if you are showing any symptoms – you must self-isolate.
See the World Health Organisation guidance on wearing a face covering.
Face coverings must cover the mouth and nose and made of cloth or other textile through which you can breathe.
General guidance states that the material must be safe to use (some materials contain dangerous fibres), breathable, removed correctly (without touching your face), washed or disposed of correctly and social distancing measures must still be adhered to. Cloth face coverings should not be placed on young children under age 2, anyone who has trouble breathing, or is unconscious, incapacitated or otherwise unable to remove the mask without assistance. Please do your research first before using a home-made mask.