A new strain of coronavirus has been detected in the UK, but is it anything to worry about?
Health Secretary Matt Hancock revealed the discovery when speaking at the Commons on Monday and went into more detail about it at a Downing Street briefing alongside England's Chief Medical Officer Professor Chris Whitty.
But how worried should we be about the mutation and what do we know about it?
What is the mutation?
Viruses mutate regularly as they try and survive and improve themselves and coronavirus is no different.
There have been many mutations of coronavirus detected throughout the course of the pandemic, and it is likely there have been countless more that have never been detected.
How do we get a new variant of Covid-19? ITV News Science Editor Tom Clarke explains
Professor Whitty said it "just so happens this one has quite a few more mutations than some other variants and that is why we've taken it more seriously."
Should we be worried?
From what we know so far, no.
At the coronavirus briefing Professor Whitty said there were three things to worry about when there was a new variant.
The first was, is it more dangerous?
Professor Whitty said there was "no evidence of that at the moment, that if you catch this variant you're more likely to have a severe disease than if you catch a different variant. "
The second is, is it invisible to the tests we have?
Professor Whitty said: "The short answer is no, the current tests work against this variant."
He said one part of the test might be slightly less effective but most will work completely normally.
The final point was does the vaccine work against it? With the short answer being almost certainly yes.
Professor Whitty pointed out that the current deployment of the Pfizer/BioNTech vaccine is still in its extremely early stages and no one will have full immunity from it yet.
He also noted a small proportion of the population had natural immunity, after previously contracting Covid-19.
He said this meant there "isn't huge selection pressure on this virus", this means the ability of the virus to select new people to infect is fairly easy, as there is no vaccine immunity and little natural immunity.
It would be "surprising" if the virus had evolved to get around a vaccine, but this could happen in the future, Professor Whitty explained.
However, there have been fears this new variant is more infectious than the initial virus and it contributed to the reason the government announced it.
But Professor Whitty said they were still unsure if this was the case.
Where in the country is the new strain?
Professor Whitty said the reason the government had detected the new variant was because "there was a good surveillance system in the UK, wider than in many other countries."
He added the new variant appeared to be focused in Kent and parts of London, both of which are seeing their cases surge.
He said: "We don't know what's cause and effect.
"Is it getting more frequent because it's in a part of the country which the rate of increase is going faster anyway and therefore, inevitably, it's a higher proportion.
"Or is it that this virus itself is more possible to transmit more easily? That is not clear."
Professor Whitty categorically denied the reason London and parts of the south east of England were being placed into Tier 3 was because of the new strain, pointing out they did not know enough about it to make an informed decision.
Mr Hancock said that while cases of the new strain were concentrated in the south east, it had been detected in 60 local authorities.
Professor Whitty said other countries had discovered something similar but they may be unrelated while others may have the same variant now in their nations which is being looked at.
He said it was unclear if it was spreading outside of the UK or if it began spreading elsewhere before it started spreading in south east England.
When did we learn about it and what happens next?
Professor Whitty said the data had been brought together very recently but some of the specimens had been taken from some time ago.
He said: "a lot of analysis had been in the past few days to try and work out what this means."
Mr Hancock said he was told about it late on Friday night and they decided to reveal it to the public on Monday.
Professor Whitty said the reason they decided to go public about it was because of the possibility it is more infectious than normal strains which would mean people would need to be even more vigilant.
As the new variant is a very recent discovery more work is being done to understand it at Porton Down, the government's top laboratory, and in other sites across the country.