• Video report by ITV News Health Correspondent Emily Morgan

The prime minister has indicated lockdown restrictions will be eased "as the science allows" after reducing the UK's coronavirus alert level 4 to 3.

Boris Johnson, speaking after Department for Health confirmed the change had been made following a recommendation from experts, said "watch this space" when asked whether social distancing for school children could be reduced in line with the alert level.

His comments came as the rate of spread of the coronavirus infection across the UK is shrinking, according to new figures published by the Government on Friday,

For the UK as a whole, the current growth rate is minus 4% to minus 2% and the estimate of the reproduction number, referred to as R, remains at 0.7 to 0.9, although it has fallen slightly in England from 0.7-1 last week to 0.7 – 0.9.

The chief medical officers of England, Scotland, Wales and Northern Ireland all recommended the level be reduced following a "steady decrease" in Covid-19 cases.

All nations of the UK, except England, have announced lockdown changes which follow the reduced risk levels:

  • Northern Ireland is reducing its two metre social distancing rule to one in schools

  • Wales is opening non-essential retail from Monday

  • Nicola Sturgeon announced a change allowing members of three household groups to meet at the same time outdoors.

Mr Johnson said: "On the social distancing measures, as I've said, watch this space, we will be putting in further changes, as the science allows."

He added: "As the alert level comes down, that will allow us to start making some progress, as I've said, on our plan and with the social distancing measures.

"So when we go forward to July 4, which is the next big stage in the plan, we hope that there will be more guidance out very, very shortly that will help people, help businesses, help hospitality to prepare for that."

Health Secretary Matt Hancock described the alert level lowering as a "big moment for the country".

Shadow health secretary Jon Ashworth welcomed the change, saying "we're obviously passed the peak of the virus", but warned "there's no room for complacency".

"This remains a very serious, deadly virus, it remains a virus which spreads with speed."

What does this mean?

In practice, a reduction from level 4 to level 3 means coronavirus is deemed less of a threat to the UK public.

The definition of level 4, which was the previous level across the country, says coronavirus "transmission is high or rising exponentially".

Level 3's warning simply states that the Covid-19 epidemic is in "general circulation".

In practical terms, this means there is a gradual relaxation of restrictions from Level 4.

Matt Hancock said the UK's coronavirus alert level reduction was a 'big moment for the country'. Credit: PA

We are seeing such moves being implemented in the four nations, with non-essential shops having already reopened or with plans to reopen.

There has also been a slight relaxation of measures which means people can see family and loved ones.

And there are plans in England to possibly open pubs, restaurants and leisure facilities like gyms and swimming pools in early July.

What are the alert levels?

The coronavirus alert system has been put in place by the UK government to signify the threat to the country posed by the disease.

There are five levels in the UK coronavirus alert system, with level five being the highest threat and level one being the lowest.

The government's definition of the five levels are:

  • Level 1 - Covid-19 is not known to be present in the UK

  • Level 2 - Covid-19 is present in the UK, but the number of cases and transmission is low

  • Level 3 - A Covid-19 epidemic is in general circulation

  • Level 4 - A Covid-19 epidemic is in general circulation; transmission is high or rising exponentially

  • Level 5 - As level 4 and there is a material risk of healthcare services being overwhelmed

Has the R number changed and what is the growth rate?

The national R number remains unchanged from last week at 0.7 – 0.9 although it has gone down marginally in England from 0.7-1 last week to 0.7 – 0.9.

On Friday, SAGE released growth rate figures for the first time. The growth rate reflects how quickly the number of infections is changing day by day.

As the number of infections decreases, the growth rate is another way of keeping track of the virus.

The current growth rate for the UK as a whole is -4% to -2%, the government says.

If the growth rate is greater than zero, and therefore positive, then the disease will grow; if the growth rate is less than zero, then the disease will shrink. It is an approximation of the change in the number of infections each day, and the size of the growth rate indicates the speed of change.

R estimates do not indicate how quickly an epidemic is changing and different diseases with the same R can result in epidemics that grow at very different speeds.

Growth rates provide different information from R estimates, but neither measure – R or growth rate – is better than the other. Each provides information that is useful in monitoring the spread of a disease.

Level change 'big moment' for UK

Health Secretary Matt Hancock said: “The UK moving to a lower alert level is a big moment for the country, and a real testament to the British people’s determination to beat this virus.

“The government’s plan is working. Infection rates are rapidly falling, we have protected the NHS and, thanks to the hard work of millions in our health and social care services, we are getting the country back on her feet.”

The level change comes following a recommendation from the chief medical officers of England, Scotland, Wales and Northern Ireland.In a joint statement, they said: "There has been a steady decrease in cases we have seen in all four nations, and this continues.

"It does not mean that the pandemic is over. The virus is still in general circulation, and localised outbreaks are likely to occur.

"We have made progress against the virus thanks to the efforts of the public and we need the public to continue to follow the guidelines carefully to ensure this progress continues."

The UK Government's coronavirus alert system. Credit: PA

Labour's Jon Ashworth said "we really need the tracking and the testing capacity in place" to ensure officials can keep the virus suppressed.

He added how people must still follow the social distancing rules and wear face masks where appropriate.

"We simply cannot take our foot off the gas, we cannot be complacent, this still remains very serious."

The relaxation of measures comes after the Office for National Statistics revealed on Thursday there had been a significant decrease in the number of people currently infected with coronavirus across the UK.

They said an average of 33,000 people in private households had the disease at any given point between May 31 and June 13, which is the equivalent of 0.06% of the total population or around one in 1,700 people.

The ONS said this was a “clear decrease” from the average of 149,000 people infected between May 3 and May 16, which was the equivalent of 0.27% of the population.

Coronavirus: Everything you need to know