It was already detected in May, that subsequent dominant strains (remember, the virus mutated with every single generation, every 10 days) have much more deletions than mutations, and are thus as such much less dangerous and much more transmissible, as their hosts don't detect it. This time UK got their sensationalist headline. In fact those are more dangerous, R is higher, and mortality is very low and insignificant. But reaching the vulnerable better makes it more dangerous in the end.