Police Dog Billy of Northamptonshire Police has been rooting out drugs, firearms and cash in the county for the past seven and a half years.
But last month, the spaniel lost his battle with cancer and died in November.
His handler, PC Ian McDonald, worked with Billy for the pooch's whole career - but also knew him as the family pet when he came home with him when they were off-duty.
PC McDonald said: "It was never a job to Billy. It was all just a game and he would do anything for his tennis ball.
"He was my best mate. He loved spending time with me and it was a difficult time when he was poorly."
PD Billy was bought by Northamptonshire Police in 2011 but quickly showed he could earn his keep.
Early into his career, a woman was injured by a shotgun blast and a man was arrested in Northamptonshire. Billy was taken to a field next to the man's house and tasked with finding the firearm.
PC McDonald said: "He made a straight line to the corner of the field. When he stopped, he was sniffing the barrel of the shotgun lying on the ground."
Billy was trained to sniff out houses and crime scenes to find drugs, firearms and cash. he would be commanded 'find drugs' and head straight for whatever he could find. If he made the right call, he would get his tennis ball as a reward.
It included a time he sniffed out a plastic bag stashed in a Northamptonshire woods that held hundreds of thousands of pounds.
The spaniel was also called on to sniff around near Buckingham Palace during the 2012 Olympics and search for firearms at Wimbledon.
PC McDonald said: "Billy helped track down an invaluable amount of criminal property in his career.
"Police dogs are an invaluable asset. In times of austerity, dogs come into their own and can find criminal property far more accurately and quicker than a police officer alone can."
After Billy died, the East Midlands Operational Support Services Dog Section tweeted a tribute to the hard-working pooch, which was met with hundreds of replies of support.