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London Mayor Sadiq Khan said he welcomed the return of the power to fine those who do not wear masks on London’s transport.
Speaking to ITV News Mr Khan said: "Today is about encouragement and education.
"Over the course of the next few days fines will be issued and there will be enforcement.
"So I would implore to Londoners and anybody using public transport across the country wear a face mask - better safe than sorry.
He added that fines improved compliance for mask-wearing.
"Today there have been staff in and around big stations in London giving out free faced masks to those who have not got one today because they don’t realise they have to wear one," Sadiq Khan said
"They should because it’s a Condition of Carriage.
"We also today have British Transport Police at major transport hubs and TfL Enforcement Officers out and about.
"Today will just be encouragement and education but over the next few days it will be enforcement and that means fines," Mr Khan added.
Face coverings have become mandatory again on public transport and shops in England under measures to combat the new Omicron variant of coronavirus.
The return of face coverings in England is just one of several new rules to come in as of 4am on Tuesday.
Travellers returning to the UK must take a PCR test and self-isolate until they receive a negative result and all contacts of suspected Omicron cases must self-isolate, regardless of their age or vaccination status for 10 days.
On Monday it was confirmed two further cases of the Omicron Covid-19 variant werefound in London, bringing the total in England to five.
The people who tested positive are not connected to each other and are not linked to the previously confirmed cases.
One case is located in Camden, north London, and the other case is located in Wandsworth, south London. Both have travel links to southern Africa.