Is it too early in the morning for some back of the envelope calculations about why things are much better than in March, and we don't need to slam on the brakes too hard straight away?

Lockdown was announced on 23rd March, and using data on deaths by date of occurrence https://coronavirus.data.gov.uk/deaths  we now know that on the 23rd, 186 people died across the UK. This continued to rise steeply, to reach 1073 people on the 8th April, by which stage 10,605 people had died.

What you'll notice is that this is only a quarter of the current total deaths. A week after the peak we were up to 16,403 deaths. Roughly speaking deaths dropped by 30% a week from then on, but the sheer height of the peak meant that it took a long time to decay at that rate.

But basically, we locked down at a much later stage than we are at now, when things were growing very fast, and so a lot of deaths were baked in already.

The upper end of SAGE's current daily growth rate estimate https://www.gov.uk/guidance/the-r-number-in-the-uk is 7% (doubling every 10 days). If we're conservative and assume that, and assume that nothing we do now has an effect for 24 days, then that gives a factor of 5.

We're at about 20 deaths/day at the moment, so under this reasonable worst case estimate, we'd be at about 100 deaths in mid October - lower than when we locked down before, and growing slower, so still more time to react.

So personally, if I were on SAGE (and thank god I'm not), I think I would be doing more or less what they are now. Dabbing on the brakes a little bit, keeping an eye on the estimate of growth rate (if it gets above 7%, we'd need to move faster), monitoring all the data.