Leading article: The military must not be allowed to set its own rules

That Sir William Gage's inquiry into the death of Baha Mousa at the hands of British soldiers did not flinch in apportioning blame is to be applauded. The Iraqi hotel receptionist was left with 93 separate injuries after two days of abuse described as "serious, gratuitous violence" that leaves "a very great stain on the reputation of the Army". Sir William is right.

But more important than the widespread condemnations of brutality that swiftly followed the publication of the Gage report – perhaps more important, even, than the apology from General Sir Peter Wall, the head of the Army – is the light that the whole sickening episode has shone on to the closed culture of the military.

Far from the exoneration that some Ministry of Defence insiders were expecting, his report is damning. The savagery meted out to Mr Mousa and fellow detainees in Basra in 2003 were not the actions of a few "bad apples". Rather, they were the result of systemic, "corporate" failures that meant neither the abusive soldiers, nor their superiors, were aware that forcing detainees to wear hoods and adopt excruciating stress positions contravened both British law and the Geneva Convention. That any British soldier is unclear about what constitutes torture is disgraceful enough. That there were others who saw what was happening and allowed it to continue is truly shameful.

The Defence Secretary has accepted the vast majority of Sir William's recommendations – including a total ban on the use of techniques such as hooding, the creation of an independent inspection regime for military detention centres, and an overhaul of soldiers' training for handling civilian detainees. According to the Army command, several of the changes are already well on the way. Rightly so. But the matter does not end there.

While the report from Sir William should be welcomed, it is deplorable that it has taken eight years for the death of Mr Mousa to be openly investigated. Indeed, the public inquiry was only necessary because the military's own internal investigations proved so unsatisfactory.

It is true that there was a court martial, in 2007, but it was a travesty. Of the seven men put on trial, all but one were cleared. And the single conviction – of a man described by Sir William yesterday as a "violent bully" who inflicted a "dreadful catalogue of unjustified and brutal violence" on Mr Mousa – carried a sentence of just one year.

More disturbing still are the repeated allegations that the military establishment actively blocked attempts to get to the truth of what happened in Basra. Even the presiding judge at the court martial talked of a "wall of silence", a "more or less obvious closing of ranks" that left the majority of those involved in the crimes not even charged.

The Gage report has thankfully forced the issue, and another 14 Army personnel implicated as complicit in the death of Mr Mousa were suspended yesterday, pending a further review. But it is grossly unacceptable that the necessary inquiries were not pursued at the time of the court martial. The military cannot simultaneously demand the unquestioning support and respect of the general public, while nurturing a culture that ranks law and justice second to protecting its own.

With another 150 cases of civilian abuse by British soldiers in Iraq that may yet come to trial, there is ample opportunity for the military to prove it has learned. General Sir Peter Wall is right when he says the death of Mr Mousa casts a shadow over the British Army. There is also a long shadow from the cover up. It is up to Sir Peter to dispel it.