  The SARS-CoV-2 pandemic peaked very early in comparison to the thresholds
predicted by an analysis of prior lockdown regimes. The most convenient
explanation is that some, external factor changed the value of the basic
reproduction number, $r_{\rm 0}$; and there certainly are arguments for this.
Other factors could, nonetheless, have played a role. This research attempts to
reconcile the observed peak with the thresholds predicted by lockdown regimes
similar to the one in force at the time. It contemplates the effect of two,
different, hypothetical errors in the data: The first is that the true level of
infection has been underestimated by a multiplicative factor, while the second
is that of an imperceptible, pre-existing, immune fraction of the population.
While it is shown that it certainly is possible to manufacture the perception
of an early peak as extreme as the one observed, solely by way of these two
phenomena, the values need to be fairly high. The phenomena would not, by any
measure, be insignificant. It also remains an inescapable fact that the early
peak in infections coincided with a fairly profound change in $r_{\rm 0}$; in
all the contemplated scenarios of data-deficiency.
