Mr Hackmann, Social Democrat Interior Minister in the region for six years, wanted to draw attention to the problems of racism and violence in the police force. In that, he has succeeded. The subject was often treated as though it were marginal - now, it is on to the main agenda and Mr Hackmann's departure has unleashed a heated discussion about police violence on the front pages and the television news.
Two incidents led to Mr Hackmann's departure. On the one hand, the beating of Dialle D, a Senegalese man who had lived in Hamburg for 10 years. The man's offence appears to have been that he was wearing a cap which bore the popular slogan 'Don't give the Nazis a chance]'.
Two drunk, off-duty policemen allegedly beat him up. They got off lightly, as though this was a minor misdemeanour. They were fined, but not suspended. There was no public trial. Mr D was persecuted for having dared to protest: his passport was confiscated, and his residence permit revoked.
Mr D was beaten up in January, Mr Hackmann heard about it in May but it was the Berlin daily, taz that exposed the affair this month. Only then were the policemen suspended. 'Something must have slipped through,' Mr Hackmann said. Then, in the wake of the controversy over Mr D, an official told Mr Hackmann about police districts in Hamburg where racism appeared to have become the order of the day. Most notably, one policeman with extreme-right sympathies was alleged to have sought a transfer to the unit dealing with combating the extreme right.
Mr Hackmann apparently decided that enough was enough and sent in his resignation - causing some to see him as a hero, as a political coward, or as a troublemaker seeking to besmirch the good name of the police. Twenty-seven police officers - all from one unit in central Hamburg - were suspended.
The police union was furious, talking of 'blind actionism', and of innocent people being branded because of 'hearsay'. Lothar Bergmann, head of the police union in Hamburg, declared: 'You don't trample on a police force whose boss you have been for six years. If something in the Hamburg police is wrong, then it is the task of an interior minister to deal with it, and not to resign.'
Mr Hackmann insisted, however, that a misplaced sense of loyalty in the force meant that it was almost impossible to get a grip on the problem. 'Every blameless official should in his own interest report the excesses of his colleagues. But this almost never happens. Mere appeals have no effect.'
Unjustified police violence is not a new theme in Hamburg. In January, Amnesty International published a report which detailed the maltreatment of detainees at one police station and emphasised the difficulty of making complaints against the police - and in bringing them to justice, even in cases where compensation was paid. The German Interior Minister, Manfred Kanther, complained of 'wholesale' accusations. But Amnesty retorted that it only highlighted individual examples in order to draw attention to a widespread problem.
Amnesty reports a stream of cases of alleged racist violence by police throughout Germany. Last month in Munden, near Hanover, a police cadet received four months' probation for giving the Nazi salute and a policeman was charged last week, after the alleged beating of an Iraqi in the eastern town of Magdeburg.
The police union has called for the latest suspensions to be reversed, arguing that the principle of 'innocent until proved guilty' has here been ignored. But an alternative police union, the Association of Critical Police Officers, argued that the problem was much more serious than the mainstream union was ready to admit. A spokesman, Bernhard Boden said: 'Many policemen have not learnt to solve conflicts, except through violence.'Reuse content