From late summer of 2020, the Welsh government used computer modelling by experts from Swansea University to try to predict the severity of future Covid waves and try to test the effects various counter-measures. So, for example, if ministers were thinking of changing rules about mixing or hospitality – this would be fed into a super computer which would try to plot what impact it would have on infection rates. Before introducing the autumn firebreak the modelling was used to see to what extent it would bring infection rates down. Prof Michael Gravenor, who led the modelling team, said ultimately the two-week firebreak worked and it took 39 days for infections to return to pre-firebreak levels. With hindsight, he said a longer firebreak would have been much more effective in suppressing the second wave further into winter. This contrasts the earlier evidence of Dr Salmon who said that firebreak was “hard to justify”.