@calneeagle and @AlistairHaimes have been analysing the various pieces of evidence: deaths, cases, 111 calls.
Based on these, it seems likely the infection peak was between 17th-19th March.
It does *not* tell us whether or not lockdown helped cases/deaths to come down even faster.
Nor does it tell us whether or not locking down sooner would have caused the peak to be earlier.