All parties said on Friday they would cease campaigning in London as a mark of respect to the victims of this terrible tragedy which left two innocent people dead.
But the pause in the election campaign didn't last ten hours - Mr Johnson put paid to that when he made a televised statement - the second of the evening - ahead of the 10pm evening bulletins saying he had "long argued" it was "a mistake to allow serious and violent criminals out of prison early".
"It is very important that we get out of that habit and that we enforce appropriate sentences for dangerous criminals, especially terrorists," he added. "That I think the public will want to see."
What we didn't know when he made that statement was that the attacker was convicted terrorist Usman Khan, who had been released early from prison - that would emerge less than an hour later when The Times front page landed.
Mr Johnson's statement was then a pre-emptive strike to try to deflect away from questions around the security services, the sentencing regime under the Conservative government and possible ministerial failings.
This strategy has been aggressively pursued by Mr Johnson over the past 48 hours.
Writing in the Mail on Sunday, he implored the public to send him back with a majority so he could change the law to ensure terrorists are not released early from prison.
He took aim at Mr Corbyn, who he said "could not provide the leadership on security this country needs" and stressed that the automatic early release laws were passed in 2008 - when Labour was in power.
There are two themes here. One is to try to shift the blame onto Labour - and raise again the "security risk" of a Corbyn government.
The second is to take a "four month" approach in which he defends his own record as prime minister while distancing himself from the nine-year record of the Conservatives in office, despite him being foreign secretary and in cabinet from 2016-2018 and an MP since 2015.
On the matter of the blame game, the row over whether Labour or the Conservative government are to blame for the laws that meant Khan was released early ensured attention was scattered rather than focused solely on the Conservatives' record in government.
Conservative ministers have also pounced on Mr Corbyn's remarks to Sky News that convicted terrorists should "not necessarily" serve their full prison sentences to plug their attack line that Labour is "weak on law on order".
Offence the best line of defence, these rows have helped obscure broader questions not just on how this tragic incident happened in the first place, but the broader Conservative record in recent years on tackling extremism in our prisons.
Ian Acheson, appointed by then justice secretary Michael Gove in 2015 to conduct independent reviews into Islamist extremism in prisons and the probation system, warned in 2016 that the parole system could not cope with terrorists but his warnings were ignored.
He made 69 recommendations but only eight made it into the final report.
He said "dozens of other urgent recommendations, many covering the sort of risk management relevant to the Khan case, I can only guess at whether they were seriously given any thought by a dysfunctional organisation [the Ministry of Justice] that was - and remains - in full-on defensive mode".
Mr Johnson is distancing himself from all that came before as he asks the public to judge him on his own record and not what went before.
And this doesn't just apply to law and order, but a wider bucket of policies.
On the NHS, there is focus on new nurses rather than the worst ever performance figures on A&E waiting times.
And on law and order, the prime minister is focusing on his new 20,000 police officers - glossing over the cuts of 20,600 police officers between March 2010 and March 2019.
On sentencing and parole, Mr Johnson is proposing tougher sentencing for the worst offenders.
However, there is nothing specific in the manifesto on these "new anti-terror laws" the PM announced overnight that would see all terrorists spend at least 14 years behind bars, which again raises questions on how much of a priority it really was before Friday's attack.
It is a teflon strategy in which Mr Johnson hopes he can uncouple from the government in which he served at the top table and from the party he leads.
Even if voters think the country is in a worse place than 10 years ago, he has to keep convincing them that he is not to blame.
And if he can't do that, his next best option is to convince them Jeremy Corbyn's Labour will be worse.
But this terror attack has knocked him off his Brexit message and onto far less sure territory.
He'll hope his own handling of this appalling terror attack doesn't put the public off him too, but politicising such a tragic event undoubtedly carries risk.
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