David Cameron appeared strained and tired today as he promised journalists he had managed to safeguard Britain from historic changes taking place in the eurozone.
The prime minister emerged from the summit in Brussels to insist he had secured the single market, delivered a job-creating patent agreement and protected the British rebate.
"It was tough securing this," he said.
Cameron said that moves towards economic and monetary union seemed to imply that a banking union would apply to all EU countries, rather than just those in the eurozone.
"That whole section of the growth compact has gone," he said.
The prime minister appeared exhausted as he sidestepped questions about the new eurozone's ability to act as an economic block and outvote Britain – a process which would eventually see business dissipate from the City of London.
"Europe is changing. There's a change taking place as countries of eurozone follow the remorseless logic [of monetary union]," he said.
"That change has consequences for Britain. My role is to make sure we have all the safeguards we need."
He added: "It's never quite clear exactly how far these changes will go. That's why when you come to the summits you've got to be focused on the text and what you're signing up to.
"Permanent vigilance is required."
Eurozone countries have agreed to create a single supervisory mechanism involving the European Central Bank and allow funds from the European Stability Mechanism (ESM) to lend directly to banks and buy bonds for struggling countries like Spain and Italy.