This case makes me very angry because it undermines the work of all those officers and staff who are out there every day doing their best to serve the public and stick to the core values of British policing. One of these core values is adopting the minimum use of force and showing restraint in the face of provocation. When tempers are being raised it is the duty of police officers to calm things down - that's what keeping the peace is all about.

This case could also undermine public confidence in what happens in police custody blocks. When I joined the police 29 years ago there was a widely held view that prisoners were "roughed up" in police cells to either get confessions from them or to exert a form of punishment. Over time many measures have been put in place to change this public view.

Video and audio recording has been installed and indeed was crucial in providing evidence in this case. The Police and Criminal Evidence Act introduced stringent rules on the way prisoners are to be treated, interviews conducted and the rights to free legal advice. Independent custody visitors were introduced; they can visit custody blocks at any time to inspect conditions and talk to any prisoner who wants to speak to them.

All this has transformed the custody process in police stations and ensured that it is about safeguarding the prisoner's welfare and collecting evidence by questioning in a totally professional manner. Officers know that if there is any suggestion that evidence has been gathered outside these rules then the court will throw out the case.

All these changes have been matched to changes in the police complaints system including a very clear standard that if any officer becomes aware of wrongdoing and stands by or does not report it then they commit a very serious disciplinary offence.

The Manchester custody case was thoroughly investigated by the force despite the fact that the prisoners involved did not want to make a complaint. There can be no cover up or any compromising of the standard for complete integrity in what we do as police officers.

Very occasionally when I have been out on patrol, members of the public have come up to me to say it would be good to go back to the "good old days" when police officers cuffed kids round the head or as one man once said to me "beat up the yobs round the back of the shops". Well this case shows why we cannot go back to those days if they ever existed. You cannot have the police being above the law or inflicting punishment themselves. This is why policing is held in such low regard in many countries of the world. Police officers have to be role models particularly to young people.

The whole process of criminal investigation is now far more professional. There is much less reliance on officers having to gain a confession from suspects through interrogation and much more emphasis on gaining other evidence from witnesses, CCTV and forensic science.

I am not so naive to think that all police officers meet the very high standards required of them all of the time. Policing is a difficult and stressful job; officers are sent to volatile situations, can suffer high degrees of provocation and in some situations threatened. Many situations are intensely frustrating with people involved who will not see reason because of their own strength of emotion or sometimes because of alcohol or mental health issues. None of this can be an excuse for any officer using unreasonable force or allowing their own temper to get the better of them. It cannot weaken our resolve to root out a very small minority of officers who are bullies and see being a police officer as an opportunity to wield power rather than to serve the public in the most professional way possible.

I spend a lot of time out with officers and talking to staff. Like every Chief Constable I started as a beat bobby and I am very much in touch with the realities of operational policing. This constantly shows me police officers and other members of staff who take great pride in what they do, show extraordinary patience and compassion and see their prime duty as building public confidence in policing. I am only sorry that their work today will be just that little bit harder because of the conduct of two of their colleagues, who are now quite rightly behind bars.