Margaret Hodge and Andrew Mitchell were quick to recognise they could succeed in forcing the government to act on financial secrecy in the overseas territories if they joined forces. The veteran backbenchers have known each other since the 1980s and their more recent political interests overlap.

Mitchell is a former international development secretary and the Conservative MP has frequently worked on cross-party lines after quitting the cabinet in 2012, advocating with the late Jo Cox humanitarian intervention in Syria. Hodge’s interest in financial transparency stems from her five-year chairmanship of the watchdog public accounts committee in the first part of the decade.

A hung parliament makes defeating the government easier, but it was not certain. Hodge and Mitchell worked together in persuading backbenchers from both sides to support their cause, arguing that forcing the overseas territories into public disclosure was both ethical and effective, before signing up the frontbenches of Labour, the SNP and the Lib Dems.

Signing up Tories was particularly important but not difficult, partly because a pragmatic Hodge was careful to emphasise that this was a policy proposed by David Cameron in 2013 before it was allowed to wither away under Theresa May. As the MP for Barking reminded the Commons: “‘If we want to break the business model of stealing money and hiding it places it can’t be seen, transparency is the answer.’ Those are not my words, those are the words of a former prime minister, David Cameron in 2015.”

Mitchell, a former chief whip, dealt with some parliamentary tactics. He refused to allow newly elected Tories to support the amendment publicly, because they could be vulnerable to reprisals or persuasion from the party whips, but the party’s ranks include a growing number of former ministers considered immune.

Ken Clarke, Nicky Morgan, Anna Soubry and Grant Shapps appeared on the supporters list last week and rebel numbers were immediately sufficient to make it clear to No 10 that a defeat on the issue was a realistic prospect. As Mitchell put it during the Commons debate: “This is evidence that, in a hung parliament, power passes from the cabinet room to the floor of the House of Commons.”