Coronavirus was brought into the UK on at least 1,300 separate occasions, a major analysis of the genetics of the virus shows.
The study, by the Covid-19 Genomics UK consortium (Cog-UK), completely quashes the idea that a single "patient zero" started the whole UK outbreak.
The analysis also finds China, where the pandemic started, had a negligible impact on cases in the UK.
Instead those initial cases came mostly from European countries.
The researchers analysed the genetic code of viral samples taken from more than 20,000 people infected with coronavirus in the UK.
Then, like a gigantic version of a paternity test, the geneticists attempted to piece together the virus's massive family tree.
This was combined with data on international travel to get to the origins of the UK epidemic.