The UK Independence Party has beaten Labour and the Conservatives to win the largest share of the vote in the European Parliament elections.
Following a storming performance, UKIP leader, Nigel Farage has said the UK had seen “an earthquake because never before in the history of British politics has a party seen to be an insurgent party ever topped the polls in a national election”.
Meanwhile, Liberal Democrats leader, Nick Clegg’s control of his party has come under further pressure after his party lost each of its MEPs, following a campaign when it had branded itself as the only party in the UK to take a pro-European Union stance.
In the early hours, the Liberal Democrats’ president, Tim Farron defended the decision to campaign on a pro-EU stand, warning that the UK is now “in danger of slipping out of the European Union”.
Meanwhile, the Euro result will put pressure on British Prime Minister David Cameron to take a more Eurosceptic line, though, so far, Mr Cameron has sought to avoid making new pledges that will box him in negotiations with other EU states.
In 2009, the Conservatives won 25 seats in the European Parliament, with 27.9% of the vote; while UKIP then took 13 places with 16.6%, Labour took 15.8% and 13 MEPs seats, while the Liberal Democrats got 13.8% and 11 MEPs.
This time, however, UKIP has led comfortably in all regions so far declared, bar London, leading comfortably in the East of England, along with strong showings in other regions, including in the South West of England.
Mr Cameron is facing pressure from some Conservatives to hold a referendum on EU membership in 2016, a year earlier than he plans to do.
In the earliest declared result from Sunderland, Labour took two seats, while UKIP took one at the expense of the Conservatives and the Liberal Democrats.
In the East of England, which was expected to be UKIP’s stronghold, the party took three of the seven MEPs on offer with over 500,000 votes.
Significantly, perhaps, tallies from Newark in Nottinghamshire - which has a by-election in early June, showed that UKIP beat the Conservatives.
In Poole in Dorset, just less than 40 per cent of voters in one county council district voted for UKIP, while in Wales UKIP finished just behind the Conservatives in Pembrokeshire.
Northern Ireland and Scotland will not report final election results until Monday, though UKIP could win one of Scotland's seven MEPs seats is being closely watched.
Indeed, some in Westminster hope for a UKIP win in Scotland - if only to block the Scottish National Party’s attempts to portray Scotland as “UKIP-free”.
Following on local election gains and increased numbers in the European Parliament, UKIP now intends to target 20 House of Commons constituencies in the 2015 general election.
The gains made by Eurosceptics elsewhere in the EU is seen as a plus by No. 10 Downing Street, which hopes that it will increase the appetite for reform.
Equally, however, there are fears that the centre-right European People’s Party and the centre-left Socialists Party will unite to drown out newly-elected Eurosceptic MEPs.
If so, and this is expected, then the European Parliament could become a significant blocking force to London-led demands for reforms.
Pressed to respond to UKIP’s popularity, the Conservatives, Labour and the Liberal Democrats are clearly struggling to come forward with new ideas.
The Conservatives believe they must do more to inform and persuade the public about Mr Cameron’s referendum pledge, though its existence is still unknown to many voters.
Meanwhile, Mr Cameron has promised speedy action to toughen welfare benefit rules that would lead to the expulsion of migrants three months after they claim benefits.
So far, Labour has issued tougher noises about immigration, but with no concrete changes on offer, while it is set to begin to start directly attacking UKIP.
Despite wobbles on Friday night in the face of UKIP gains, when some Labour MPs began to criticise leader, Ed Miliband, the party regained some of its poise over the weekend.
The late-emerging confidence occurred after a detailed opinion showed that Labour has made major gains against the Conservatives in key battleground seats.