Britain's plan to move to the final phase of unlocking society is on a knife edge. The target date of 21 June is in the balance.
The rapid spread of the so-called Indian variant of Covid-19 - and its potential to outpace the rollout of vaccines in the UK – is now at a critical point.
Within a few short weeks, the risk of opening up society, the economy and travel has gone from manageable to potentially catastrophic.
It presents Boris Johnson and his government with a real dilemma. Evidence gathered in the next few days will determine whether this is a decision point as critical as the ones faced last March and September that we heard so much about in Dominic Cummings' evidence on Wednesday.