There was much at stake in the Old Bailey trial of Abu Hamza al-Masri. The four-week proceedings raised uncomfortable questions all round. Could “incitement” ever be the basis for a successful prosecution? Is Britain a haven for extremists, and if so why? Why was Abu Hamza allowed to continue preaching hate so publicly for so long? Why had he been allowed to become a totemic figure in British Islam? His conviction yesterday for incitement to racial hatred and murder has provided some answers.

First, it is worth saying what the trial was not about. As Mr Justice Hughes emphasised in his summing-up, it is not an offence to describe living in Britain as a “toilet”, as Abu Hamza had. Nor is it an offence to suggest that Western societies are corrupt and without moral value. But the prosecution succeeded in demonstrating beyond reasonable doubt that Abu Hamza’s outpourings of bile overstepped not just the boundaries of taste, decency and liberal tolerance but also those of the law. At a time when the limits on free speech are at the forefront of our national debate, the jury delivered an unambiguous verdict: preaching that the killing of non-Muslims was justified in any circumstances, “even if there was no reason for it”, as Abu Hamza put it, was not just beyond the pale but also beyond legality.

The verdict will to some extent counter Britain’s reputation overseas as a soft touch for suspected terrorists and preachers of hate. Tolerance is one of Britain’s finest hallmarks. But a small number of spokesmen for radical Islam, such as Abu Hamza, have used the sensitivity shown towards their position and religion to abuse our national broad-mindedness and willingness to extend the benefit of the doubt. A clear line has now been drawn. We do have the legal means to combat hateful individuals.

One of the unanswered questions relates to why Abu Hamza was not prosecuted earlier. Police and MI5 had been watching him for years. Yet he was initially arrested on an extradition request from US authorities, and only subsequently charged by their British counterparts. The verdict will perhaps encourage officers to intervene more promptly in cases where radical clerics are abusing their position to rally their flocks to hatred and killing.

The largest issue is for Britain’s Muslims. Some may contrast yesterday’s verdict with the partial “not guilty” decision won last week by Nick Griffin, the British National Party leader, on charges of stirring up racial hatred. But any suggestion of moral equivalence should be resisted. Mr Griffin is a reprehensible character with loathsome views. Yet the case against him was, unfortunately, weak. Abu Hamza preached murder at a mosque attended by Zacarias Moussaoui, the accused “twentieth 9/11 bomber”, and Richard Reid, the shoe bomber. It also hid a cache of weapons and encouraged a generation of suicide bombers.

Abu Hamza’s conviction offers an opportunity for British Muslims. In his defence, he claimed he was encouraging Muslims to stand up for themselves. This they should do, but by denouncing the fanaticism he breathed in the name of their religion. Rather than perpetuate the image of victimhood that he thrust on them, Britain’s moderate and rightfully proud Muslims owe it to their faith to denounce Abu Hamza for the thug he is and set about repairing the image of Islam from the damage he has inflicted on it.