David Cameron is expected to win just enough seats to secure a small working majority and although the electoral dust has yet to settle, conservative right-wingers are already manoeuvring to put pressure on the prime minister to move swiftly on establishing a referendum on continued EU membership.
Cameron's unexpected victory and his ultra-slim majority - virtually all the major UK polling groups were predicting a hung parliament, with no overall party gaining enough seats to form a majority on their own - will strengthen the position of the party's large backbench Eurosceptic right-wing.
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And without the restraints of a pro-EU coalition partner such as the Liberal Democrats, Cameron will come under further pressure from within the Eurosceptic wing to act on his pledge to hold an in/out referendum by 2017.
However, the other major election result of the night - the Nationalist landslide victory in Scotland - means Cameron may well have to backtrack on his Brexit promises.
A Conservative - or from a Scottish viewpoint an 'English' - push to leave the EU could initiate a Scotexit rerun from the resurgent pro-EU Scottish Nationalists.
European commission president, Jean-Claude Juncker however, has thrown Cameron a lifeline of sorts, saying recently that he was open to Cameron's arguments for some kind of EU treaty change that could necessitate the need for a Brexit referendum.