When the video, leaked to ITV news, was aired on Tuesday night, Labour advisers and leader Keir Starmer were preparing for Wednesday’s PMQs in his parliamentary office, which looks over the river Thames.
They were running through the script for what they did have planned when one adviser popped out to watch the news, while others started to see the reaction to the video on Twitter.
One person present said the reaction was, in the first instance – silence, as they sat there in “utter disbelief”.
Within minutes they knew they needed to react, ripping up their plans for PMQs, while Starmer raced over the road to deliver his immediate thoughts on camera.
Watch the full exchange between Ed Oldfield and Allegra Stratton in the mock televised press briefing
It was a mirror to the shocked mood in Downing Street, after a week in which they had parroted the same line repeatedly – that all guidelines were followed and that there was no party.
They too began with silence – and then they stuck with it - with the highly unusual move of failing to put forward any ministers for the morning round as they scrambled with how to react by lunchtime on Wednesday.
And yet, Wednesday is the first anniversary of the vaccine programme – the moment the health secretary was going to mark a year of the single biggest success this government can shout about.
Instead, broadcasters lined up to explain why he wasn’t taking his seat.
Rather than vaccines, Boris Johnson will be bombarded Wednesday by questions about why he appears to have lied repeatedly about a party taking place in Downing Street – but also what the implications will be for public health messaging now.
ITV News UK Editor Paul Brand reports on how the leaked footage adds fresh weight to accusations of rule breaking levelled at Downing Street
After all, you don’t need to go to opposition parties to find angst about this. Take the Tory MP Charles Walker, who said to me this morning that Downing Street must now aim for people to “sensibly mingle and mix with family and friends by exercising their own judgement”.
“This has to be the way forward because they government’s ability to mandate anything in law is now greatly diminished,” he added.
So many Tories agree with him – even ministers and those in the Cabinet - with some admitting that resignations will have to come – even if not at the top level.
Those loyal stress that Boris Johnson wasn’t at the party, but many of his advisers were there that night and he’s had a week to investigate things.
When I asked one senior Tory source why they kept denying it – he said simply: “They thought they could get away with it.”
And to some extent maybe they could’ve done before Tuesday. Until this broke, a number of new Tory MPs across the north and Midlands said to me that they had so far had pretty light mailbags on this issue – nothing compared to the Dominic Cummings scandal. But that could change.
One of the 2019 intake texted Wednesday to say: “Whatever happened was obviously totally inappropriate given the sacrifices everyone else was making. I hope there will be a much fuller explanation and apology in short order.”
Another MP who has been in the party for many years said, the PM’s “problem now is getting out of last week’s dispatch box denial”. And not just at the dispatch box – but repeatedly to television cameras and even last night.
The Conservative MP Sir Roger Gale argued that if the PM can’t clear this up at PMQs – then this could not only match Barnard Castle – but surpass it.