Rules on wearing masks have returned to London in a bid to curb the spread of the new Omicron variant of coronavirus.

Measures come into force today (November 30) with face coverings again becoming compulsory in shops and settings such as banks, post offices, hairdressers and public transport.

In addition, all travellers returning to the UK must take a PCR test and self-isolate until they receive a negative result.

Prime minister Boris Johnson has said Covid-19 vaccines and boosters remain the best line of defence.

He said: “The measures taking effect today are proportionate and responsible, and will buy us time in the face of this new variant.

“Based on everything we know, our vaccines and boosters remain our best line of defence, so it is more important than ever that people come forward when eligible to get boosted.

“Not only will today’s steps help us slow down the variant’s spread, but they will help us protect each other and the gains we have all worked so hard for.”

People not wearing masks in public will be fined £200, and the fines double with every offence, up to a maximum of £6,400.

Under the current guidelines however, face coverings are not required in venues such as cinemas, theatres, pubs and restaurants.

Though, The Royal Shakespeare Company (RSC) has re-introduced mandatory face coverings which must be worn in the theatre and during performances.

Students in year 7 and above, school staff and visitors have also been "strongly advised" by the Department for Education to wear masks in communal areas, unless exempt.

The measure, which takes effect from today, applies to all education establishments as well as childcare settings, such as early years care.

All contacts of suspected Omicron cases must self-isolate, regardless of their age or vaccination status.

The Joint Committee on Vaccination and Immunisation (JCVI) is now advising that all adults aged 18 to 39 should be offered a booster dose of the Covid-19 vaccine, in order of descending age groups, to increase their level of protection.

Those aged 40 and over are already eligible for a booster vaccine.

The JCVI said booster doses should be given no sooner than three months after people have had their second dose of an original vaccine – shaving three months off the current six-month wait.

In further advice, young people aged 12 to 15 should be offered a second dose of the Pfizer/BioNTech Covid-19 vaccine, no sooner than 12 weeks after their first dose.

A spokesperson for the NHS said: “The NHS will contact you when you are due to book in for your lifesaving booster vaccination, and when you get the call, it’s vital that people come forward as quickly as possible."

The measures in place are described by Number 10 as “temporary and precautionary”, and will be reviewed in three weeks.

England’s deputy chief medical officer Professor Jonathan Van-Tam told a Downing Street briefing on Monday that the booster campaign has “never been more vital than at this point in time”.

Prof Van-Tam said scientists around the world agree that the Omicron variant is “of increased concern”.

He said there are still uncertainties about how transmissible the variant is and its impact on severity of disease.

He said the “number of mutations present, already on first principle, makes us worry about a possible effect on vaccine effectiveness”.

He made clear that there “are far more things we don’t know yet, than things we do know” about the variant, but that he expects more to become clear in three weeks.

MPs will debate and vote on new Covid restrictions in England, including face coverings in shops and public transport, today.

A number of Tories are deeply unhappy at the prospect of a return of controls – but with Labour backing the measures there is little chance of a government defeat.

Meanwhile, working from home is not compulsory.

For a list of where you need to wear a mask, visit