Even at the end, he still had them talking. For the best part of a quarter century, Gordon Brown has had the political press corps either scratching its collective head, trying to divine his latest tactical gambit, or else making a gag at his expense. As Brown formally announced his intention to stand down as an MP after a 32-year Commons career, some speculated that the timing was a classic Brownian ploy to sabotage preparations for George Osborne’s upcoming autumn statement, a last bit of partisan news management by a master of the art. Others said it was typically Brown in another sense: the re-announcing of news he’d already pre-announced last week.

And yet the word, when it came, was rather different from what Gordon-watchers have grown used to. It was more personal, for one thing. He delivered it in the Old Kirk in Kirkcaldy, in the shadow of the church where his father, one of the defining influences on his life, used to preach. At his side were wife Sarah and their two sons, the boys so rarely glimpsed that when they appeared with him on the day he left Downing Street in May 2010, the sight was a jolt to those who’d never before conceived of Brown as a father.

The truth is that the British public rarely got to see the man in full. But what they saw loomed large enough. Brown was indisputably a big beast, a towering figure in Labour and British politics for almost two decades. His former spin doctor, Damian McBride, may well be right to observe that “as a feat of sheer endurance, no modern politician will ever again match Gordon Brown’s 18 years at the top of his party”. Named as John Smith’s shadow chancellor in 1992, he remained at the helm – either sharing the wheel with Tony Blair or steering on his own – until 2010.

Even this year, in what was meant to be the twilight of his career, he has been a dominant figure. When he took to the stump in the closing months of the Scottish referendum campaign, Ed Miliband may have been around but there was no doubt who looked like the leader of the Labour tribe.

But it’s more than longevity that’s made Brown so compelling. Bill Clinton was once described as the most psychologically complex inhabitant of the Oval Office since Richard Nixon. In Downing Street that honour surely fell to Brown, the most complicated prime minister since Winston Churchill.

The darkness was well documented, the anger that had him hurling phones and staplers, stabbing car seats and firing off emails in the dead of night. There was a strain of Nixonite suspicion of rivals and enemies; he could be rudely dismissive of colleagues; he was famously destructive in his dealings with Blair, his one-time co-conspirator. Once he was prime minister, insiders spoke of a paralysing indecision. Even admirers detected a gnawing insecurity.

And yet, all those notorious psychological flaws have to be squared with a personal charm that was, fatally for him, invisible to the camera. It comes coupled with a quality that is not quite emotional intelligence as conventionally understood, but something rather deeper. Brown knows how to speak to those who have suffered, perhaps because he has endured more than his fair share of misfortune himself. He can demonstrate great empathy and wisdom, capable of showing a human understanding that confounds the television caricature.

Still, it’s not on any of this that his reputation will depend. Ultimately, his place in history will turn on achievement rather than personality. To be sure, he begins at a disadvantage: the man ejected from office after only three years at the top. Future historians may well say that fate was avoidable, if only he had not ducked the election that never was and which Brown might well have won in 2007.

Any future judgment will take a dim view too of the mistakes he made as chancellor. His proclaimed end to boom and bust was ridiculous. He let the City run wild for too long (though few said so at the time). He made a Faustian bargain with the priests of high finance, allowing them to build their castles of cash on sand in return for tax revenues he could divert towards schools, hospitals and the poor.

He naively thought the roulette wheel in the City would keep turning and the house price bubble keep floating, forever. It’s also true that instead of borrowing, he should have run a surplus in the later years of the boom.

But that’s only one side of the ledger. On the other stands his adamantine refusal to surrender to Blair’s enthusiasm for British membership of the euro. Today’s Eurosceptics rarely give him the credit, but it was the iron chancellor and his five tests, designed to be unmeetable, that kept Britain out of the single currency. He was denounced at the time – not least by his impatient, thwarted neighbours in Downing Street – but few would now deny he was right.

When the great crash broke, as the key players in the US administration later admitted, it was Brown they turned to: Brown who, at the critical hour, came up with the plan to recapitalise the ailing banks. When the G20 came to London in April 2009, Brown was in the chair, winning agreement for a $5tn stimulus to the world economy, a move widely credited with preventing a global recession tipping into a global depression. No wonder the august Brookings Institution later declared the London G20 “the most successful summit in history”.

And then, in 2014, the intervention in the Scottish referendum, built on the realisation that the argument had been framed the wrong way: as Scotland v Britain rather than as two competing visions of Scotland. Brown grabbed the no campaign with his bare hands and turned it around, closing with a speech that was Brown at his best: eloquent, passionate, fiercely intelligent.

By rights, that last achievement should have restored his reputation sufficiently to make him a candidate for the final role he covets, a big international job, perhaps leading the IMF. But even without it, he has secured quite a legacy. He may not have saved the world, but Brown can legitimately claim to have saved the pound, the global financial system and the union.

Coupled with his own frugality – he refuses even to take his prime ministerial pension – it makes the contrast with Blair intriguing. The latter was always projected as the winner of the pair, the smiling sun to Brown’s brooding cloud.

Blair was indeed a winner, the charismatic face of New Labour, victorious in three elections. But his epitaph will for ever be Iraq. The great twist in their decades-long rivalry is that it might eventually be Brown’s record that looks the stronger.