The author of the study described here is Nicholas G. Davies London School of Hygiene and Tropical Medicine.

I think the BBC article plays the findings about increased transmission a bit down - the authors say that the mutated variant seems to spread exponentially with 50% to 70% per week, even under a lockdown. This would explain why in London, which is now in tier 4 lockdown, over 60% of the new infections are now by the new variant.

One must be cautious that the data is still very noisy.

Here is a twitter thread which summarizes the paper (preprint) - it is worth looking at:

https://twitter.com/_nickdavies/status/1341845176361349123

Here is the preprint:

https://cmmid.github.io/topics/covid19/reports/uk-novel-vari...