Mayor Sadiq Khan said enforcement of face covering rules on the Underground, buses and other services run by Transport for London would be increased after they were made compulsory again by the Government from 4am.
Mr Khan said: “Provided with proper enforcement powers, TfL will now be able to work with policing partners and really boost compliance on the network, with the selfish few who refuse to wear a face covering facing a penalty fine.”
Face masks will also be mandatory in shops, banks, post offices and hairdressers as ministers seek to slow the spread of the Omicron mutation.
Health Secretary Sajid Javid added: “I know that Londoners will play their part and look out for each other by wearing a face covering when in a shop or on transport.”
All travellers returning to the UK must also take a PCR test and self-isolate until they receive a negative result.
Scientists fear Omicron, which is believed to have first spread in southern Africa, may be better at evading vaccines and transmit more quickly than Delta, currently the dominant variant in the UK.
Three cases of Omicron have so far been confirmed in London, in Wandsworth, Camden and Westminster, with several more “highly probable” ones.
TfL compliance officers and police will be able to issue £200 fines in coming days for first offence of not wearing a mask, with the penalties rising for repeat offenders.
Transport chiefs are sending out reminders that customers travelling on the TfL transport network must wear face coverings for the duration of their journeys or risk being fined, unless they are exempt.
In other developments:
Dr Jenny Harries, chief executive of the UK Health Security Agency, urged people to get protected against Covid and advised “not socialising when we don’t particularly need to” to slow the spread of Omicron. She told BBC radio that there had been five confirmed cases of Omicron in England with ten “highly probable”, and the number was expected to rise. Nine have been confirmed in Scotland.
Asked whether England would see a return to work from home guidance, she told BBC Breakfast: “The whole point about the booster programme and the introduction of mandatory face mask wearing in enclosed public spaces is exactly to try and avoid that.”
Pfizer’s chief executive Albert Bourla told US channel CNBC: “Within 95 days, basically we will have a new vaccine (against Omicron).”
Boris Johnson defended England’s new coronavirus rules, saying: “The measures taking effect today are proportionate and responsible, and will buy us time in the face of this new variant.”
Professor Adam Finn, a member of the Joint Committee on Vaccination and Immunisation, said now is a “time for caution” as he urged people to do “anything that they can do to reduce the risk” of catching Covid-19.
Striking a different tone from the scientists, health minister Gillian Keegan advised that people should “go about your plans”, families should be able to attend school nativity plays, but people shoud follow the new rules. She told LBC Radio: “Obviously, you know, wear a mask, be cautious.”
Richard Walker, managing director of the Iceland supermarket, backed the return of mandatory mask wearing but said staff would not be “policing” its enforcement.
Wearing a face mask has been a condition of travel on TfL services since the legal Covid restrictions were relaxed in mid-July but they were not mandatory by law as they had been earlier during the pandemic.
However, the tighter regime was reintroduced this morning meaning people who flout the rules will be able to be fined in coming days.
Teams of TfL enforcement officers were despatched across London today and swooped on commuters failing to wear face masks on transport.
Officers stopped those ignoring the rules and warned them they would face fines next time.
The Transport Enforcement teams were at hubs including Stratford, Canning Town and Victoria and were also patrolling buses, trams and DLR trains.
Officers at Victoria shouted “face coverings are mandatory on the network” as commuters passed through.
A member of the Enforcement team told the Standard: “Most people listen and are very good and apologise. We have had belligerent people in the past but today we are asking people politely and they are responding well. Maybe they have missed the news or something, so we are giving them a chance.”
Most commuters welcomed the enforcing of the rules.
Margaret Traynor, 60, said: “People should respect the rules. I’m glad TfL are stopping people.”
Georfe Savides, 22, said: “It’s an important message. I’m young but of course you have to wear a mask to protect others.”
One man who was stopped told the officers: “I’m sorry I just wasn’t thinking. I won’t forget in future.”
Some claimed medical conditions but in general welcomed the intervention of the officers.
At Waterloo notice boards were set up around the station and ticket officers were seen reminding people of the mask rules.
On the Jubilee Tube line a rough estimate found that eight in ten commuters were wearing masks.