Ambrose Evans-Pritchard of the Telegraph makes the case:
"What a momentous day for British democracy. The era of presidential rule is over. Parliament has reclaimed the powers chipped away by successive prime ministers ..... It has even snatched some powers it never had, beyond control of the purse. There can be no going to war on executive authority alone, or by Royal Prerogative. Britain's living Constitution has been refashioned before our eyes, in seven hours of exhilarating debate".The last time this happened in Britain was 1782 when Parliament chose to give up suppressing the American revolution, over protest of the Prime Minister who represented the King's interest.
A realistic alternate view is that Britain lost its way in a muddle of easily-swayed opinion and pride. From a NYT article:
“The real reason the vote was lost was not so much doubt about strategy as the toxic nature of association with the United States, the idea of being dragged along again like a poodle in a U.S.-led military operation,” said Jonathan EyalUpdate: "Britain has helped Obama rediscover the Constitution. No need to thank us, America"