Pupils and staff at secondary schools across the country are being 'strongly advised' to wear face masks in communal areas.

The guidance from the Department for Education has come after Boris Johnson announced tighter measures after cases of the Omicron variant were found in Essex and Nottingham.

A third person has tested positive today.

The UK Health Security Agency (UKHSA) said it had identified the third case of Omicron in an individual with links to travel in southern Africa, who visited Westminster in London before leaving the country.

From tomorrow, the Department for Education are "strongly advising that face coverings should be worn in communal areas in all settings by staff, visitors and pupils or students in year 7 and above."

The rules will be reviewed in three weeks.

Pupils should continue to wear face coverings on public and dedicated school transport, unless they are exempt.

Education Secretary Nadhim Zahawi said: "The news of a new variant – the so-called Omicron variant – will have understandably caused concern for people across our country, including our teachers, wider education and childcare staff, parents, pupils and students.

"We are already taking targeted and proportionate action as a precaution while we find out more information about the new variant. As we do so, we will continue to prioritise children’s and young people’s education and wellbeing, making sure education and childcare settings are as safe as possible and children continue to benefit from classroom teaching.

"This worrying situation, however, emphasises the need for better support from the Government for the education sector.”

"We are working with education and childcare settings to enhance safety measures where needed, including introducing isolation for 10 days for close contacts of suspected Omicron cases.

"I’d like to thank everyone working to support our children and young people for their patience and hard work.

Twice weekly lateral flow tests are still being encouraged and those who come in to contact with someone should take a PCR test but do not need to isolate unless they are over 18 and unvaccinated.

However, anyone who comes into contact with the Omicron variant should isolate for 10 days regardless of their vaccine status.

Geoff Barton, general secretary of the Association of School and College Leaders, said it supported the measures “as a sensible response to the risks posed by the Omicron variant of Covid-19”.

But he added: “This worrying situation, however, emphasises the need for better support from the Government for the education sector.”

Following the discovery of a third Omicron case in the UK, Dr Jenny Harries, the UKHSA chief executive, acknowledged it is “very likely” that further cases will be found in coming days.

The Omicron strain is feared to spread rapidly and may evade existing vaccines to a degree.

Targeted testing is being carried out in locations where the latest positive case visited while likely to be infectious, as well as in Nottingham and Brentwood, Essex, where the first two cases of Omicron were identified.