From daytime drug searches through the streets of Camden with sniffer spaniels to a search for suspected armed criminals in the dead night with 'track and attack' German shepherds, we follow these canine cops and their human partners on the front line of the battle against crime in London.

This week, Send in the Dogs looks at the work of the British Transport Police who make thousands of miles of railways and tubes safe for commuters. The program follows Rafa, the sniffer spaniel looking for drugs, Charlie who accompanies police on house raids looking for cash and the work of crowd control police dogs patrolling football matches.

Send in the Dogs this week looks at the extraordinary work of the West Yorkshire police unit. On the trail of drugs with Bella the sniffer dog, Otto hunts for a car thief on the run, trouble in the maternity ward as Beth the German has an emergency dash to the vets and incredible story of Jac, the tracker dog that catches killers.

London's canine cops take on the capital's crooks as the Metropolitan Police use their elite dog squad to crack down on crime. Diesel, the Metropolitan Police's Cocker Spaniel, who can find drugs, cash or guns in a "nanno-second" helps the TSG and his handler, PC Adele Gibson, raid a suspected drug den. Sgt. Pete Madden and his German Shepherd, Brodie, go after car thieves.

There is no margin for error as Greater Manchester Police dog squad go after car thieves who have earned the city the title of Car Crime Capital of Britain. PC Rogers and Leo, the German Shepherd, show how clearing the streets of car criminals means looking in the strangest places