Those who talk of the ‘radicalisation’ of Jihadi John, the British recruit who does the voiceovers for Islamic State decapitation videos in the sort of mockney accent American girls reportedly find irresistible, are missing one blindingly obvious point.

There is no meaningful sense whatsoever in which Mohammed Emwazi can be categorised as a radical. He is very much a political reactionary, and indeed a living exemplar of the dictionary definition of that word.

Of course both concepts – like many other elements of contemporary political discourse, including left and right as points on an ideological spectrum – trace their origins back to the French revolution.

The designation ‘reactionary’ refers to one who advocates a return to an earlier social order. There can surely be no more accurate summation of a movement out to secure the restoration of an Arab variant on feudalism, directly modelled on the seventh century.

It is a mistake to see IS as some latter-day national liberation movement acting under the guise of religion, a twisted reincarnation of the FLN or Viet Cong or Umkhonto we Sizwe, resorting to armed struggle to secure an essentially just end, and thus in possession of some claim on the moral solidarity of the western left.

Its is a movement of theocratic totalitarianism that aims is to impose, by force of arms, an absolutist reading of Islam of anyone unlucky enough to come within its grasp. The parallel drawn by Kenan Malik with the long-forgotten creed of nihilism strikes me as at the very least a suggestive one.

As IS has already shown in the territory in which it holds sway, it is ready to murder religious and sexual minorities, violently enforce patriarchy, destroy non-Muslim antiquities and to amputate and execute for infractions of its particularist interpretation of sharia. The kicker is, it wants to extend its domination across the entire planet.

Asim Qureshi of advocacy group Cage yesterday described Emwazi as “extremely kind, gentle and soft-spoken, the most humble young person I knew”.

It cannot be excluded that he once really was a smashing bloke who used to give his mother flowers and that, and only wanted to visit Tanzania out of a burning desire to witness giraffes in the wild.

But Emwazi is now a suspected mass murderer, complicit in and very likely responsible for taking at least seven lives for the benefit of the camera.

To brand such actions as ‘radical’ runs against every usual connotation of a word coined by a whig politician in 1797 to describe a demand for electoral reform.

Radicalism ever since have generally been a description of patrician progressives, dispensing benefactions de haut en bas to the grateful masses.

In British history, the phenomenon has been broad enough to encompass Tories such as Oastler and Liberal radicals such as Lloyd George.

But most reasonable people would recognise the difference between advocating factory legislation and pensions, and hacking the head off a hapless taxi driver seeking to deliver aid consignments to Syria.

More recently, ‘radical right’ has sometimes been used as a label for post-fascist formations such as Italy’s Alleanza Nazionale and France’s Front nationale, although most political sociologists prefer to call these parties populist right.

It does not usually fall to me to insist on fairness towards such unpleasant figures as Gianfranco Fini or Marine Le Pen, but they have worked within the democratic process to secure their ends. Not even that applies to Jihadi John.

The boundaries of radicalism, then, clearly are somewhat flexible. But they should not be stretched beyond breaking point.

Aneurin Bevan once noted that a reactionary was ‘a man walking backwards with his face to the future’. Let us be clear that Emwazi is precisely that, and that is not the least of the reasons why the left should not be lining up behind his apologists.

David Osland is a London-based journalist and writer