The allegations that police officers might have used waterboarding on suspects sounds like something from a 1970s cop drama rather than the working practices of a police unit today.

Stories of police brutality were commonplace 30 or more years ago and it took the exposure of notorious miscarriages of justice, such as the Birmingham Six case, to bring such wrongdoing to light.

Allegations of the ill-treatment of prisoners are much less common today. The truth is that gratuitous violence by police officers against suspects is rare. The ongoing inquiry suggests, however, that it might not have been eradicated.

My time in the Metropolitan Police included a stint as a senior officer in anti-corruption command. That experience taught me that corrupt police officers are most commonly motivated by two things.

The principal spur is financial gain — the temptation to steal knowing that the word of a police officer is more likely to be believed than that of a suspect. The second motivation is the misguided belief that it is better to get a conviction by fair means or foul than to let someone seemingly guilty go free.

A false confession, extracted under duress, might be seen by some officers in this target-driven age as a short-cut to achieving detection targets. It might also avert a move away from detective work because of lack of productivity.

Such ideas are corrosive and have to be tackled robustly. The centrepiece of any anti-corruption strategy is a deterrent policy that encourages internal whistleblowing. What better source of information than a tip-off, which can then be investigated? For this to happen, colleagues need to be confident that there will be no retribution and the bosses will stand by their pledge to root out corrupt officers.

Alongside that, there must be trip wires to catch corrupt officers. Dedicated anti-corruption teams will spend hours trawling through the records of colleagues who have attracted high levels of complaints. In exceptional cases, covert operations may be mounted to test an officer’s behaviour.

But such inquiries are expensive and do not produce results that induce public confidence in policing. The investigation of police corruption tends, therefore, to be a cyclical affair. In contrast, corrupt practices tend to be permanent.

The ebb and flow of the internal police response means that at times it is more difficult to be corrupt, but not impossible. The temptation to corruption, though, is always there. No commissioner or chief constable can ever afford to take their eye off the ball.

Andy Hayman is a former assistant commissioner in the Metropolitan Police

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