It’s a widespread view in Westminster that, of the Leader of the Opposition and the Shadow Chancellor, it’s the latter who is more dangerous.

The idea seems to have started on the basis that John McDonnell is more extreme than Jeremy Corbyn – praising the “bombs and bullets” of the IRA, rather than just lending them friendship and political sympathy; calling himself a Marxist and throwing the Little Red Book, rather than bothering to dress up his dogma as mild social democracy; openly demanding “a situation where no Tory MP…can travel anywhere in the country or show their face anywhere in public without being challenged by direct action”, rather than paying lip-service to “kinder, gentler politics”.

That’s probably correct, but it’s only part of the reason to be concerned about him.

As well as his more hardline views, McDonnell is also more intelligent than his friend and leader. Even the Labour Party seems aware that this is visibly the case. When Corbyn is caught out in unwise associations with deeply unpleasant people, Labour’s official excuse is almost always that he was simply too dim to realise what he was doing. He didn’t know who those wreaths were for; he called racist terrorists “friends” without meaning it; it never occurred to him that the ‘diplomat’ from a hostile totalitarian state who was extremely keen on chatting to him might be a spy, and so on.

They never try such lines for McDonnell, however – which seems an implicit concession that while blundering might be plausible and forgiven (rightly or not) in their leader, his sidekick does not have the air of a man who does things by accident.

McDonnell has exhibited his wiles in the gradual evolution of Labour’s economic policy, and his careful adjustment from a firebrand trolling the established order to the possible Chancellor who seeks to destroy it. He has developed a fascinating style, with a tone that simultaneously discusses his ideas as if he was recounting the details of a pretty standard commute, inevitable if intermittently engaging, while dropping in the details and references which communicate clearly to the faithful the true radicalism of what he is suggesting. It was there in his speech to Labour conference today, in which he launched a policy described by The Guardian (albeit approvingly) as “a declaration of class war”.

We all know the underlying problems of Corbynomics (McDonellomics is too ugly a word to tolerate). They cannot tell us where the money will come from to take over all the industries they want to run. They cannot explain to us how the people who made a loss on their own music festival will be capable of directly controlling large swathes of the economy. They cannot square the circle of raising vastly more through taxation and debt, while supposedly also accelerating growth and wages. They cannot, in short, overcome the problems which these ideas has suffered every time it has been tried in the past.

McDonnell, however, has chosen simply not to get into all that. He waves it all away as “costed” (which it isn’t) and instead chooses to set his own media agenda. The pre-briefing of his speech set up a row with business groups about the deterrence of investors that would be brought on by seizing and giving away shares and profits. The addition into the speech itself of plans to arbitrarily fire and replace the senior managers of all nationalised industries has sparked another such battle which will likely run into tomorrow morning’s news.

The critiques of these policies are no doubt reasonable, and the critics’ concerns are well-founded, but that is to miss the point. The Shadow Chancellor not only doesn’t care, he desires the complaints – he disagrees, obviously, but more than that he wants a chance to perform in an exhibition match in which he can beat up people whom his target vote dislike. Destroy investors and purge bosses? Yes please. Who else? Let’s throw in a crack at the press for having the temerity to scrutinise his leader, for good measure. His audience lap it up, and his targets oblige by sticking out their chins for him to punch some more. So yes, he’s dangerous – all the more so because he is clever.