This is a really helpful article laying out the striking features of this new variant - eg 17 of the 23 mutations seem to have been acquired at once,(“unheard of”) - and also the risks of jumping to final conclusions too early in the investigatory process https://www.sciencemag.org/news/2020/12/mutant-coronavirus-united-kingdom-sets-alarms-its-importance-remains-unclear

There is no doubt that in some Regions (notably London/Kent/ Essex) the variant has quickly become dominant

The variant B1.1.1.7 was first identified in 20/9/20.
It accounted for c.26% of cases by mid-Nov

By the week commencing the 9th of December, London, over 60% of all the cases were the new variant.

It has also cropped up elsewhere in the country in 60 LA areas, but is not the dominant variant in all of them, including in areas with fast rising infection and high positivity.

This striking evolution is thought likely to have occurred during the long infection of an immune compromised patient who has since died, going through an extended period of fast evolution with multiple variants competing for advantage.

In particular there are 8 mutations that encodes the spike protein on the viral surface, two of which are particularly worrisome. One has been shown to increase how tightly the protein binds to the ACE2 receptor (the entry point to the human cell).

The other leads to the loss of 2 amino acids in the spike protein, and has been found in virus that elude the immune response in immunocompromised patients.

A particular type of PCR test used in the U.K. Labs - TaqPath- normally detect 3 genes. But one of the mutations lead to a negative signal...just 2 show up...which made tracking B.1.1.7 easier.

I am not clear if ALL U.K. labs use the same TaqPath PCR test.

So back to that “may have increased the virus transmissibility by up to 70%” . It seems this was based on modelling by Nervtag.

Christian Drosten, the German virologist in Berlin says that the claim was premature and that the rapid spread might be down to chance.

He reminds us of a flurry of alarm over the Spanish variant in the summer that scientists at first thought was more transmissible, but no longer do. It just spread as people moved around more.