The UK Independence Party (UKIP) is not so much a populist party that became Eurosceptic as a Eurosceptic party that became populist. However, careful tracing of a sequence that began in the late 1990s reveals that it was not UKIP but the Conservative Party that first fused populism and Euroscepticism. David Cameron’s decision in 2006 to temporarily abandon both approaches, just as Nigel Farage became UKIP’s leader, turned out, in historical institutionalist terms, to be a critical juncture. It provided UKIP with an opportunity to fill the gap, after which the Conservatives were unable, as Europe was hit by successive economic and migration crises, to regain the initiative. As a result, and as Cameron’s coalition government failed to meet its promises to control immigration, UKIP enjoyed increasing electoral success. This allowed it to exert significant, if indirect, pressure on the Tories, eventually helping to force Cameron into promising an in/out referendum – a promise that did neither him nor his party any good. The UK case, therefore, reminds us that anyone wanting to understand populist Euroscepticism needs to appreciate that the relationship between the radical right and its mainstream, centre-right counterpart is more reciprocal, and even symbiotic, than is commonly imagined.