The post of UN secretary general is a prestigious but frequently thankless role. It also tends to be filled by men (it has always been men so far) who achieve their global status through their office, not on their own merit, and who appear to be wearing a suit slightly too big or too grand for them – they don't quite live up to the job, in other words.

In recent years we have had Kofi Annan – saintly, but ineffectual – and Boutros Boutros-Ghali, whose chippiness would have been amusing, were it not so serious. (He wondered whether British criticism of him, you will recall, was "because I'm a wog".)

And now we have Ban Ki-moon. Leave aside that he looks like the mild-mannered provincial bank manager of ancient stereotype. Here is what he's been up to recently.

Yesterday he opined of the elections in Burma, scheduled for 7 November, that unless the military regime released all political prisoners, "then there may certainly be some issue of legitimacy or credibility". Well, you don't say, Mr Secretary General.

Next he ended a trip to Cambodia after being ambushed by Prime Minister Hun Sen's announcement that the current UN-backed tribunal trial of four leading Khmer Rouge leaders will be the last. No more of Pol Pot's followers will face justice. Hun Sen – himself ex-Khmer Rouge – doesn't believe in turning over any more stones. You don't know what you might find underneath. Oh, and would Mr Ban mind shutting the UN's Cambodian human rights office while he's at it? There's a good fellow.

Where else has he been of late? Thailand, where, according to the Bangkok Post, he courageously declared that the country's long-standing and bloody confrontations between the Red and Yellow Shirts was really none of his business. That was "an internal affair and the Thai people must settle the problem on their own", apparently.

Regular readers will know that I'm not much in favour of western politicians jetting in to developing nations and giving them the benefit of their callow advice (cf: David Miliband in India last year). But for those of us who hope against hope that the UN can be a credible body and an influence for the good, the role of secretary general is crucial.

He – or maybe, eventually, she – has to inject the role with clout through the force of his own personality. The secretary general has to be so impressive that, in future, a Mandela, say, will consider the job an important one, and not a step down from having been chief executive of their own state.

If Ban secures another five-year term – his current one concludes at the end of next year – that day will be even further off. Until then, it's all hail the mediocrity-in-chief.