evidence: Constitution Unit, Department of Political Science, University College London , London, [...] As is now well known, the Prime Minister’s 2017 general election gamble backfired. Labour performed better than expected, and the result was a hung parliament and minority Conservative government. May agreed a ‘confidence and supply’ arrangement with the Northern Ireland Democratic Unionist Party (DUP), with whose support she would enjoy a notional Commons working majority of 13. In theory, this agreement extended to Brexit matters. [...] This was a predictable outcome based on a previous attempt by the Commons to choose between multiple options on Lords reform in 2003 (McLean et al., 2003)—as was widely mentioned at the time.