Det Supt Moffat has played a key role in ensuring murderers and child abusers have been jailed after joining Northamptonshire Police to safeguard the public.

His investigation of historic child abuse in East Northamptonshire in 2001 led to several men being jailed for their attacks on young boys which dated back 20 years.

And among the significant and high profile investigations he has led, one resulted in a change in national policy on the restraint holds used on young people in custody, following the death of Gareth Myatt at Rainsbrook Training Centre, near Rugby.

For Det Supt Moffat, who joined Northamptonshire Police in June 1979, the learning curve never stopped.

He said: "You learn from every case you deal with. No training can prepare you for everything and you learn to deal with what you are faced with.

"The horror that some of the murder scenes present is quite traumatic."

One such case was that of Joan Biggs, who was raped, murdered and set on fire on a cooker in Northampton. He also led the hunt for missing teenager Sarah Benford who disappeared, aged 14, nine years ago.

Another memory which sticks in his mind was his role as family liaison officer for the Spencer family following the death of Princess Diana, which he describes as the busiest week of his career.

Det Supt Moffat worked in the Homicide and Major Crime Team and more recently, has led several investigations into police corruption, including one involving the Metropolitan Police last year.

He said: "For all officers one of the worst things is to find their colleagues have not only breached the trust of the public but also the friendship and camaraderie of the police service.

"Organised criminals are only too ready to target officers and try to infiltrate our organisation – that's an emerging trend, trying to place people into the service as officers or members of staff."

Det Supt Moffat said some of the biggest changes he has seen in 30 years has been the development of communication technology and advances in DNA.

He said: "There is continuing demand from the public for faster responses. We also didn't used to have an armed response unit in the county 24 hours a day. I think there is undoubtedly more crime being committed by those who need to fuel drug abuse."

Det Supt Moffat, 49, also said the changes to licensing laws have not resulted in the cafe culture the Government had in mind.

While he is stepping down from police work, his investigations continue as he is setting up a consultancy firm focusing on misconduct across the public sector.

He added: "I have enjoyed enormously serving with Northamptonshire Police. Policing remains an excellent career."