The UK is now a multi-level polity with asymmetrical minimum ages of enfranchisement. The franchise was first extended to 16- and 17-year-olds in the 2014 Scottish independence referendum. The Scottish and Welsh governments now permit 16- and 17-year-olds to vote in elections to their devolved parliaments and local councils. The Northern Ireland Executive and the devolved authorities in England do not, however, have the power to change the voting age, and across all four nations of the UK, the age of franchise remains 18 for elections to the Westminster Parliament. The previous extension of the age of franchise, from 21 to 18 in 1969, attracted little controversy or political partisanship. But while there has been considerable political consensus regarding voting age reform in Scotland and Wales, debate over Votes-at-16 for Westminster elections has witnessed growing party-based partisanship. This article draws upon elite interviews with politicians across the political spectrum elected to Westminster and the devolved institutions on their attitudes to voting age reform, conducted as part of a 2-year Leverhulme Trust Lowering the Voting Age in the UK project. The article argues that the multi-level party politics of the Votes-at-16 debate has consolidated rival party opinions on voting age reform at Westminster but not beyond.