They have been called the Lennon and McCartney of politics: visionary harbingers of generational change, international A- listers with a global following, formidable partners so intertwined it is hard to think of one without the other.
But British Prime Minister Tony Blair and Chancellor of the Exchequer Gordon Brown may wince at the analogy. After all, John and Paul's harmonies eventually gave way to discord and dissolution. And Britain's foremost political relationship has long since fallen flat.
Every few months a new set of anecdotes swirls around Westminster, detailing the strident antipathy that supposedly divides the prime minister and his right-hand man.
Yet for all the attention given to conflicts between Brown and Blair, their relationship is perhaps most remarkable for what it has not done: create gridlock. Indeed, the rivals have presided over what has been, by most measures, a fairly ambitious and quite functional government.
The situation puzzles political observers. After all, dissident acolytes are little tolerated in other polities. It's hard to imagine Presidents Bush or Vladimir Putin sitting back while a rival schemes for their job.
With Britain heading for a likely May general election that Labour is expected to win again, the longstanding rivalry raises several questions. Why has it festered so long? And why has Blair not dispensed with his turbulent chancellor?
'We Can Work It Out'
"Life is very short," sang John and Paul, "and there's no time for fussing and fighting my friend." Political life is even shorter, but so far Blair and Brown have not let rancor end their careers.
The press have dubbed the bickering the "TB-GBs." Some say it dates to 1994, when Blair leapfrogged Brown to lead the Labour Party, making his old friend a mere sidekick.
The strange quality to this rivalry is that both men know they need each other.
Brown has an impressive eight-year economic track record that has undermined the claim that Labour cannot manage the economy. Subdued inflation, high employment, low home-loan rates, successful antipoverty measures - it's a list that Blair himself praises.
The chancellor of the exchequer is also more popular with traditional Labour, a constituency Blair cannot afford to alienate, particularly as many are still unhappy about the Iraq war.
"That is the difference between the prime ministerial and presidential systems," says John Curtice, professor of politics at Strathclyde University in Glasgow, Scotland. "Mr. Brown has his own power base within the party and cannot be ignored."
But Brown likewise cannot do without Blair. The telegenic prime minister is still more likely to appeal to wavering, middle-class voters than his aloof, intellectual counterpart. One commentator has likened it to the fable of the frog and scorpion, …