Face coverings will be mandatory in shops and supermarkets from Friday.

Under the new rules, people will need to have their nose and mouth covered or face a fine of up to £100.

People with certain disabilities will be exempt.

This comes after rules requiring people to wear face coverings on public transport became mandatory last month.

Initially many experts and authorities, including the World Health Organisation (WHO), suggested face coverings were not effective in preventing the spread of Covid-19 but are now recommending wearing them in indoor spaces.

– Has there been confusion over the new rules?

Yes, opposition MPs have said it needs to be clarified whether customers have to wear face coverings in takeaways and sandwich shops in England.

The criticism came after days of mixed messages with the Health Secretary and Boris Johnson’s official spokesman contradicting each other on the matter.

The Daily Telegraph reported early on Thursday that people using sandwich shops and takeaways will be required to wear a mask, and buying food from the counter and then sitting down to eat inside the shop will be banned.

But the Government refused to confirm the report ahead of the formal announcement.

– What does the science say about face coverings?

A report recently published by the Royal Society suggests that even basic homemade face coverings can reduce transmission if enough people wear them when in public.

The study, based on mathematical modelling, showed that if an entire population wore face coverings that were only 75% effective, it would bring the R value, which is the number of people an infected individual passes the virus on to, from 4.0 to under 1.0, without the need for lockdowns.

Another Royal Society report suggests the use of cotton masks is associated with a 54% lower odds of infection in comparison to the no mask groups, when tested in a healthcare setting.

Melinda Mills, Nuffield professor of sociology, at the University of Oxford, told a webinar: “So that should suggest that when you’re generally in the public that it should offer you some, not 100%, but it does offer you some protection.”

Meanwhile, another study which looked at coronavirus deaths across 198 countries found that nations which had policies favouring mask-wearing had lower death rates.

In another piece of scientific research, published in the journal Proceedings of the National Academy of Sciences last month, scientists calculated that wearing face coverings prevented more than 78,000 infections in Italy between April 6 and May 9, and more than 66,000 infections in New York City between April 17 and May 9.

– What are the benefits to wearing them?

Experts say the risk of coronavirus transmission appears to be higher in poorly ventilated indoor spaces and wearing face coverings in small shops or enclosed shopping centres could help reduce the spread.

Keith Neal, emeritus professor of the epidemiology of infectious diseases at the University of Nottingham, said: “Lack of strong evidence of their effectiveness should not be considered a problem but the evidence is accumulating that they have a part to play in reducing transmission and also in protecting the wearer.”

In addition, there is also increased evidence which suggests that many people with the virus who do not have symptoms can still be contagious.

– What do people need to know about wearing masks?

Ideally the face coverings should be made of multilayer high quality cotton.

Where possible they should be should be worn in indoor confined spaces and crowded spaces, especially where social distancing cannot be maintained.

Japan follows the three Cs, closed spaces, crowded places, and close-contact settings.

When wearing a face covering, it should cover the mouth and nose with no gaps.

– Are some face coverings better than others?

The Who advises a three-layer face covering in the community – the outer layer should be water resistant, the inner should be water absorbent and the mid-layer acts as a filter.

It emphasises that a face covering alone cannot protect people from Covid-19, and must be combined with social distancing of at least a metre and regular hand washing.

The Government has said coverings can be made from scarves, bandanas or other fabric items, as long as they cover the mouth and nose.

But scientists at the Leverhulme Centre, who studied different types of face coverings used by members of the public, say some coverings are not as effective as others, with loosely woven fabrics, such as scarves, shown to be the least effective.

Prof Mills, director of the Leverhulme Centre, said: “Attention must also be placed on how well it fits on the face; it should loop around the ears or around the back of the neck for better coverage.”

What are the main messages about face coverings?

Prof Mills says cloth coverings are an effective way to protect the wearer and those around them.

She says that face masks and coverings cannot be seen in isolation and are part of a package that involves hand hygiene and social distancing.

Consistent and effective public messaging is vital, she concluded.