Timeline:

1st week of May
Rumours started circulating in media & govt: Dominic Cummmings had broken lockdown restrictions on more than one occasion.

10th May
Boris Johnson arbitrarily, & against scientific advice, changed Govt slogan from “Stay at Home” to “Stay Alert”.
https://twitter.com/nicktolhurst/status/1265610287102730240

2/

Was also in 2nd week of May that Boris Johnson moved away from the very idea of restrictions as the driving force of UK strategy on Coronavirus and instead focussed on the idea of “common sense”

At no point did any scientists - epidemic or behavioral - agree with this plan.

3/

While there’s no reason a slogan can’t be changed during a heath campaign - experts were left confused as:

1. Lockdown phase hadn’t finished yet
2. “Stay Alert” doesn’t mean anything in epidemiological or even health terms

Only one explanation makes sense...

4/

The only explanation that makes sense is the replacement of “Stay at Home” slogan with the nebulous “Stay Alert” motto was a political choice..

..a political choice made by a PM whose chief advisor had been caught flouting the “Stay at Home” restrictions the week before.