It must be appalling to find yourself subjected to arbitrary detention. You would have no power to challenge said detention. You would have no idea when, if ever, you would be set free. And that concept is reflected in the first of five definitions offered by the UN working group on arbitrary detention: “when it is clearly impossible to invoke any legal basis justifying the deprivation of liberty”.

But that was not the reason they gave for their opinion that Julian Assange has been arbitrarily detained in the Ecuadorian embassy. His detention fell foul of their third definition; when “non-observance ... of the international norms relating to the right to a fair trial ... is of such gravity as to give the detention an arbitrary character”.

That opinion was backed by three of the five members of the working group. A fourth felt she could not take part because she, like Assange, is an Australian. So it fell to the fifth member of the group, Vladimir Tochilovsky, to point out the flaw in the majority’s reasoning.

They had assumed that Assange had been “detained in the embassy of Ecuador by the authorities of the United Kingdom,” the Ukrainian lawyer wrote. In fact, the Wikileaks founder had fled bail in June 2012 and used the embassy “as a safe haven to evade arrest”. Fugitives often do that, Tochilovsky pointed out. But “premises of self-confinement cannot be considered places of detention for the purposes of the mandate of the working group”.

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That is so self-evidently true that it seems hard to believe the majority could have been persuaded otherwise. Assange has always been free to leave the embassy at any time.

Of course, he knew he would be arrested for breach of his bail conditions. Of course, he knew he would face extradition to Sweden. Of course, he knew that he might face extradition to the United States once proceedings in Sweden were at an end. But that does not mean he was detained, and still less that his detention was of an arbitrary character. How, then, did the majority of the working party get it so wrong?

First, they said he had been detained in prison for 10 days in 2010 “at the very beginning of the episode that lasted longer than five years”. They claimed “the arbitrariness is inherent in this form of deprivation of liberty”. This is palpably absurd. Assange was detained pending possible extradition. If his detention had been arbitrary he could not have challenged it, and been released on bail. But that not was what happened. The three-and-a-half years he has spent as a fugitive from justice cannot affect the lawfulness of his original imprisonment.

According to the working group, his 10 days in prison was followed by 550 days of house arrest. He suffered “harsh restrictions”, including tagging and restrictions on staying out overnight. Harsh restrictions?

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And then we get to the fatal flaw. The working group considers that Assange’s stay at the embassy “should be considered as a prolongation of the already continued deprivation of liberty”. Its members provides no justification for this leap of logic.

Assange’s argument is that he was granted “diplomatic” immunity by Ecuador. But the UK does not recognise the notion that a state can merely designate as a diplomat anyone, of whatever nationality, and they are then exempt from the general law.

Fortunately, the working group does not seem to have been taken in by this notion. Instead, the majority base their opinion on the length of time that has passed, as if to say that a fugitive is entitled to avoid justice by merely hiding away for a few years.

If Assange is extradited to Sweden and charged with rape, there is no reason why he should not receive a fair trial. Any disadvantage he may suffer through the delay is entirely down to him. He has not been subjected to arbitrary detention. The idea that he should receive compensation for hiding himself away in Knightsbridge – as the working group says – simply heaps offensiveness on absurdity.