They said a real estate mogul with an implausible bouffant and a reality television show could never become US president. They said that a maverick mayor with the nickname of "Duterte Harry", after the gun-toting cop Clint Eastwood played in a series of violent films, could never be elected leader of the Philippines. And until recently, it was said that a plummy voiced MP who has not held a ministerial role, and with a manner so old fashioned that he has been called "the honourable member for the 18th century", could never become the leader of Britain's Conservatives.

And yet Donald Trump and Rodrigo Duterte did indeed win the highest offices in their respective lands, and now Jacob Rees-Mogg is being taken seriously as a contender should Theresa May step down as the UK's premier and Tory leader. As Professor Philip Cowley of the University of London put it last week, referring to Mr Rees-Mogg’s popularity with the party members who have the ultimate say: "If he stands in any forthcoming leadership election, if he gets through to the last two, he'll walk it."

Mr Rees-Mogg is known for his civility and excellent debating skills. But it was previously deemed preposterous that a man who used to campaign with his nanny and who is unashamedly patrician, in defiance of an almost rigidly egalitarian popular culture, could move from the margins to being a serious contender.

Then again, no one believed that a bearded vegetarian from the far left could ever have hopes of occupying No 10 Downing Street. As Tony Blair told an interviewer in 1996, the year before Labour finally returned to power in Britain: "You really don't have to worry about Jeremy Corbyn suddenly taking over." It turns out that most people were wrong in both cases.

What all these men have in common is the appearance of authenticity, and it seems that popular hunger for that quality is far from abating. This is a worldwide phenomenon, for whatever the failings of Russia's Vladimir Putin, Turkey's Recep Tayyip Erdogan - or indeed Mr Trump, Mr Duterte or Mr Corbyn - there is no denying that what is perceived as their no-nonsense, straight talking approach has considerable appeal.

It would not be correct to label them all as anti-politicians, since many have been in politics for a long time. But they all represented a break with previously established norms: from the chaotic liberalisation of the Yeltsin years in Mr Putin's case; from Kemalist secularism in Mr Erdogan's; and from the longstanding dominance of the centre left and right in Mr Corbyn's.

The appeal of authenticity - of appearing not to care if what they say is politically incorrect, of if they look or sound unfashionable - is often linked to the rise of populism, which is generally regarded as worrying. (Although I would make two points about that. Firstly, that in a democracy it really is up to the people to decide who they want to vote for, and if they wish to be represented by populists, why shouldn't they? And secondly, that warnings about populists are nearly always about parties of the right. Populism, it seems, is quite benign if it's on the left.)

But unlike populists who want to break the system entirely, it is notable that all the examples I have listed above have risen through the system. None have come from nowhere. Mr Trump may be a very unusual president, but he is still a Republican. Mr Erdogan's AKP has been in office for so long they can in no way be considered outsiders, and in any case the movement was born from the ashes of a previous Islamist party that had governed Turkey for a couple of years in the 1990s. Mr Rees-Mogg is rising through what may be the most successful and longest-established political party in European history.

The pattern emerging is that the appetite for disruption is undiminished. What should give cheer to those worried about populists is that disruption from within the mainstream appears to be enough to satiate that desire; and if that is the case, then the real extremists are likely to lose out. If Jacob Rees-Mogg did become Tory leader, for instance, the UK Independence Party (not all of whose members are extremists) would surely close shop.

For all his talk of “draining the swamp”, President Trump has found he is able to do business with both the leader of the Senate, Mitch McConnell, and of the House of Representatives, Paul Ryan. Both are pretty right wing, but they represent what is now the Republican mainstream. They are in. Steve Bannon and his alt-right friends are out.

In France, President Macron pulled off the extraordinary feat of successfully presenting himself as a force for disruption – from the centre right, which is about as mainstream as it gets. His victory over the National Front’s Marine Le Pen, as I have argued before, may have been less impressive than many said; but her party has failed badly in elections since and is unlikely to regain its previous momentum any time soon.

If disruption is here to stay, the challenge then is for mainstream parties to harness that force. Familiar (over-familiar) faces such as Germany’s Christian and Social Democrats are failing to do so, and are ceding that vote-pleasing ground to extremists. To fight back established parties must rise to a difficult, but not insurmountable the task: they must be the change that the people so clearly still want to see.

 The writer is a senior fellow at the Institute of Strategic and International Studies Malaysia