we covered it on the forum way back, probably June.
The high point for fatalities was April 8th (by date of death - reporting high point I think was 10th) and there is a 4 week lag from infection.
April 8th minus 4 weeks gives us a high point for infections around 10th March.
Partial lockdown 21st March (pubs) and full lockdown announced 23rd March evening effective 24th and the effect on infections wouldn't be feeding through until 1st week April and the effect on deaths would not feed through until 20th April.
By then deaths had been falling for almost 2 weeks.
Friday 20th, wife was working as normal in her factory with no measures other than hand sanitising points. Shops were open.
The main earlier effects had been cancelling of flights to overseas destinations from around a week earlier and schools had closed that week prior to pubs closing.
But pre 10th March we really had done diddly squat and pre 21st/23rd it was lockdown light.
A paper was published by a Bristol Professor late Spring charting the peak infections pre lockdown and SAGE have assessed the high point of cases in March at up to 100,000 a day - I personally suspect it was higher - but we didn't have testing among the general public then.
I hope my summary helps.