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I was being serious. Distributionally, most of the cases were 1-2 days before the error was spotted. To be clear though, when I said "not much impact", I didn't mean that people might not die because of it, only that it wouldn't affect the large scale functioning (such as it is) of the tracing operation.

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> Distributionally, most of the cases were 1-2 days before the error was spotted.

That’s always true though if the virus is spreading exponentially (dunno whether it currently does in the UK).

This is more true than it would be from pure exponential growth alone, especially the relatively slow exponential growth the UK as a whole currently seems to be seeing (doubling time maybe about a fortnight?) The issue was effectively dropping all results after a certain number from a particular location, so at the start relatively few results were dropped and it was spotted around the time that number started to become substantial. It's that hard cutoff where results suddenly start to be dropped that means most of them are in the last few days.

Sadly it takes about 24 to get tested and 24 hours for the lab result. That gives very little time to trace contacts before they start entering the asymptomatic-but-infectious-to-others stage. A one day delay is a problem.

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