If government ministers were not initially worried about Sir Graham Brady’s amendment for next Wednesday’s debate on the renewal of the 2020 Coronavirus Act, then they are now. Last Tuesday, Steve Baker, who has been whipping support for it, revealed that the “the magic number” of Tory MPs to defeat the government had been reached. But this translates into a Commons majority only if the Opposition parties vote with the Tory rebels.

Labour has made the strategic decision to enable the necessary votes in the Commons. Among the senior Labour MPs adding their names to the Brady amendment are Harriet Haman, John Spellar and the chair of the parliamentary Labour party, John Cryer. Rapport between the Labour whips’ office, individual MPs and the leader of the Opposition’s office is now tighter than the frayed bonds of communication between Tory whips, backbenchers and Downing Street.  Crucially, Labour joins a Tory rebellion that has expanded far beyond the ERG Spartan veterans of former civil wars to all wings of the Conservative party who want to regain its role as a player rather than a spectator to government diktat. Also on board are DUP MPs.

This move by Labour is still a gamble, not least with public support. “Leave the government to own their mess” is a popular sentiment among those close to Keir Starmer. But they also know that the party does not want to get on the wrong side of a seemingly pro-Lockdown public, in addition to its instinctive support for many of the restrictive measures enraging Tory MPs.

It is helpful that the Brady amendment’s Tory backers cannot be glibly dismissed as the eternal awkward squad and the breadth of exasperation has made it easier for Opposition parties to join it.

This is important because Keir Starmer’s strategy involves positioning Labour as a force of moderation that is guided by the national interest. The extent to which he has pursued a “constructive opposition” path in which Labour has backed the government’s Covid-suppression strategy has limited his lines of attack in the Commons but chimes with mainstream opinion in the country.

The last thing Brand Starmer wants is to be contaminated with accusations of vulgar opportunism – that the sober statesman (“he had a real job prosecuting criminals before politics”) is ready to enjoy a cheap thrill in the company of Tory diehards, just to to play parliamentary games.

is the Brady amendment really his Verdun – ground he feels he cannot surrender regardless of the cost?

Labour, however, appears to have calculated that supporting the Brady amendment comes without reputational cost. Many Tory backbenchers may be unhappy with the sweep of powers their government is amassing in the control of the nation’s economic and social welfare but this is not explicitly the amendment’s purpose. The wording supports the retention of the Coronavirus Act – and the powers conferred by the 1984 Public Health Act – but merely requires that “parliament has an opportunity to debate and to vote upon any secondary legislation with effect in the whole of England or the whole of the United Kingdom before it comes into effect.”

This is an easy sell for any Opposition MP – the right to improve the quality of ministerial diktat by debating and approving it before it is signed into law rather than accepting it as a fait accompli after the event.

John Smith’s Labour Party suffered no reputational loss to its European credentials by trooping into the same lobbies as Teddy Taylor and Bill Cash and the other Maastricht rebels when there was gain to be had at the expense of John Major, as it did against Theresa May’s Withdrawal Agreement even although it kept the country aligned to more EU regulation than they could possibly have hoped for. Supporting the Brady amendment is even easier – for it is about holding a Tory government to better account. If you’re a Labour or SNP MP, what is not to like about that?

Much now depends on how the Speaker will interpret the propriety of appending Brady’s qualifying statement to legislation that was not designed to be amendable. If it goes ahead, the government has a choice between climbdown or humiliation. Like so much in the Covid votex, there is no profitable option for Number 10. Folding is weak, and will encourage more dissent; but standing, fighting and losing, is worse. When even some of the prime minister’s own officials suggest that he’s scarcely involved in many of the decisions currently being taken in the Cabinet Office, is the Brady amendment really his Verdun – ground he feels he cannot surrender regardless of the cost?