Prime minister's questions sketch
By Guto Harri
BBC political correspondent
This can't have been his dream birthday.
Waking up as prime minister - yes. Having the first pre-dawn coffee in the study of Number 10 - most certainly.
A birthday smile from Mr Brown
But half-an-hour at the despatch box being mocked and hounded by people he hates - I doubt it.
Celebrating 57 years on the planet is no excuse, however, to avoid the House of Commons, and just before noon - Gordon Brown squeezed past cabinet colleagues to take his place at the despatch box.
He did so like a condemned prisoner, clutching a shabby pile of papers, plastered with post-it notes in yellow, orange and green.
Flash of teeth
No leather sheath as a birthday present then. No organised file like that carried confidently by his predecessor, whose dream birthday probably did involve holding his own in a hostile environment and showing off to the cameras.
Gordon Brown has been around long enough not to expect any generous gift from David Cameron. And, for a second he looked unnerved when the Conservative leader wished him a happy birthday.
Off they went again - on that familiar pattern - ending with a bizarre exchange of insults.
Grave faces cracked into smiles along the front bench. There was a flash of teeth from the prime minister, as his colleagues cheered.
Highlighting the anniversary - of course - was the first dig of the day by David Cameron - reminding all of us that there's a decade and a half between the two leaders.
But there were two other attacks to come today.
"Enough of that", said Mr Cameron, before turning into an aggressive inquisitor, seemingly outraged that the government had taken a year to follow up Dutch warnings about dangerous criminals on our shores.
The pattern afterwards, is now well established.
Mr Cameron asked about the "catastrophic" failure to check DNA data
David Cameron poses questions which make Gordon Brown look incompetent and indecisive. Gordon Brown avoids the question and poses his own to his opponent, as if the Conservative leader's failure to answer a straight question is more embarrassing that his own.
The only relief on his birthday was not taking a blow over Northern Rock. The Liberal Democrats did raise that issue, but Mr Brown didn't seem to mind that.
It was then that I witnessed the man-to-man stare across the despatch box. The prime minister had carelessly suggested Mr Cameron was too embarrassed to raise questions about the Rock.
Mr Cameron smiled, tapped his notes, and mouthed the menacing words - I've got some questions here.
Within minutes, he was on his feet. "He wants a Northern Rock question... here's one for him", and off they went again - on that familiar pattern - ending with a bizarre exchange of insults.
David Cameron said the PM's record on freedom of information would make Fidel Castro proud.
Gordon Brown attacked his opponent for engaging in "student politics". There was laughter all round - but who were they laughing at or with?
After all that, most of us would head off for a good lunch, drowning all memories of another miserable parliamentary session in our favourite wine. Not this prime minister.
Gordon Brown headed off to deliver a speech on citizenship. Later on he'll greet so-called champions of climate change.
And tonight? A party? Dinner with friends? A night out with his wife in one of the world's best cities. His subdued spokesman suggests that would be frivolous, and predicted "a quiet evening with the family".