Gordon Brown heads to Portugal for his first EU summit as prime minister today, as the union's 27 heads of government attempt to find agreement on the controversial EU reform treaty.
Worryingly for Mr Brown, a poll in today's Financial Times found that 75% of people in the UK want the prime minister to hold a referendum on the treaty - something he refuses to do, despite calls from the Tories, the rightwing press and some trade unions.
harbours Referendums in France and Holland killed off the treaty's forerunner, the EU constitution, in 2005.
Labour went into the 2005 election promising a plebiscite on the constitution, but Mr Brown maintains that the new reform treaty is sufficiently different from that document not to require one - and emphasises that he has secured "red lines" exempting Britain from any changes not in the UK national interest.
A separate poll in today's Daily Telegraph found that only 6% of Britons accepted this argument.
According to the FT poll, 61% of British people describe themselves as "not at all familiar" with the contents of the treaty, which would reform the EU's institutions in light of the arrival of 12 new member states since 2004. Four per cent described themselves as very or extremely familiar with the document.
If true, this would mean an impressive 2.4 million Britons could take you through the intricacies of how the treaty would change the EU's voting procedures, expand the roles of its president and foreign policy chief, and give more scrutiny powers to national parliaments, among other things.
The Telegraph poll found that 69% of Britons wanted a vote on the treaty, including 57% of Labour supporters, while the FT poll also found that 76% of Germans, 72% of Italians, 65% of Spaniards and 63% of French people wanted a referendum.
Our correspondents will be blogging from the summit with the latest developments throughout the day.
What's at stake?
As I made my way to the airport at 6am this morning, the BBC was describing Gordon Brown's first EU summit as prime minister as "the big one".
The stakes for the British premier are high. While at home he is facing charges of "blatant dishonesty" proclaiming the EU treaty is fundamentally different from the EU constitution abandoned two years ago, on the continent fellow member states are said to be disgruntled that Britain has clinched such a good deal.
Jim Murphy, the UK's Europe minister, told me yesterday that not only did the treaty not amount to a constitution, but if agreed, it would mean there would not be an EU constitution "in my lifetime".
Certainly, the new agreement does away with proposals for supernational symbolism such as anthems and flags. But in many other respects it is essentially the same.
Because of this, the argument goes, it amounts to little more than a reforming document and no referendum is required.
Not so, claimed Labour MP Gisela Stuart earlier this week. It was she who accused the government of dishonesty over the two differences between the constitution and the new treaty.
As one of the "wise men" who helped draw up the original EU constitution, she can hardly be accused of merely being Eurosceptic.
Mr Murphy claimed he hadn't seen Ms Stuart's comments when I asked and refused to be drawn on that argument.
But he did concede that Westminster's European scrutiny committee was right when it said there may be some financial cost in using some of our red line opt-outs.
Although Britain could not be fined for using its opt-outs it would have to meet the cost of doing so.
1.15pm: The temperature in Lisbon today is 26C. It's like a beautiful English summer's day.
The press centre at the summit is the size of a vast aeroplane hangar, with huge banks of desks colonised by country - the British delegation is grouped right at the back.
Journalists from every British national newspaper and TV station are present.
Gordon Brown is due to attend a reception for European socialists this afternoon. So a group of us have ventured out of the press centre to find out where he is.
We've arrived at a building that resembles an empty art gallery. A section of the room has been roped off for the press and cameras are assembled outside. But as yet no guests have arrived.
2.15pm
So, after almost an hour of waiting, Gordon Brown certainly wins the prize for the grandest entrance.
While many of his counterparts arrived slowly in dribs and drabs, Mr Brown was the last to arrive, sweeping in with a cavalcade stretching as far as the eye could see.
The premier was greeted by Jose Socrates, the current president of the union, and Louis Amado, Portugal's minister for foreign affairs.
But within minutes of Mr Brown's grand arrival, the party was broken up for more private talks upstairs.
3.30pm
We've just had a briefing from Mr Brown's official spokesman. He tells us all is going to plan.
The prime minister followed his meeting with the European socialists with bilateral talks with Mr Socrates, and he is next due to speak with Romano Prodi, the Italian PM.
The actual summit starts at 6pm. Discussions will apparently continue over dinner, which is due to start at 8pm.
One of my Westminster chums has managed to get hold of the menu:
Crepe of vegetables to start, grilled sole and saffron rice for main, followed by chocolate cake with strawberries. And all of this will be washed down with Cartuxa Portuguese white wine - unfortunately we don't know about the red...
During the briefing, Mr Brown's spokesman was asked whether the PM watched last night's football matches - apparently Mr Brown had the TV on "in the background" of his office for both.
While some suspected Tony Blair's love of football was only skin deep, Mr Brown's passion for the sport remains undisputed.
On Saturday he will be in Paris to watch Britain in the Rugby World Cup final as a guest of the French president, Nicolas Sarkozy - but that is two days off, and it looks like tonight could be a late one if Poland and Italy make their grievances heard.
6pm
Have just updated the Guardian's main EU story on the back of Gordon's on-camera press conference. In the flesh the PM is looking his most confident and "robust".
The basic thrust of his comments (and I paraphrase) is that we've got what we came here for, which means there is no need for a referendum.
Asked if he thought he could win a referendum, Mr Brown, not surprisingly side-stepped the question - that was one bear trap he wasn't about to fall in to.
All other questions he batted away, repeating ad nauseam his claims about the red lines and protecting British sovereignty.
One journalist tried to move the agenda on by asking Mr Brown if he had taken the opportunity to speak to the Portuguese prime minister about Madeleine McCann.
Mr Brown said he would be raising it with him later.
10pm
News just in: the Poles are apparently 'digging their heels in'. A deal on the treaty is not expected until the morning.
