Lepppard began his police in 1984 when he joined Surrey Police as a constable.
He served as a traffic officer in the early years of his career.
In 1989, he was promoted to sergeant and trained as a detective.
As a senior investigating officer, he investigated a number of murders including the contract killing of Mario Commatteo.
By 2003, he has risen to become the area commander of North West Surrey in the rank of chief superintendent.

In 2005, he transferred to Kent Police as an assistant chief constable with responsibly for specialist operations.
In September 2005, he became assistant chief constable with responsibly for area operations.
He led the investigation into the Securitas depot robbery that had occurred in February 2006.
In December 2007, he was promoted to deputy chief constable.
From March until July 2010, he was serving as temporary chief constable of the force.

In January 2011, he left Kent Police to join the City of London Police as Commissioner.
In addition to leading the City's police, he was head of the National Fraud Intelligence Bureau.
In the 2012 New Year Honours, he was awarded the Queen's Police Medal.
He retired on 31 December 2015 and was succeeded by the force's Assistant Commissioner, Ian Dyson, QPM.

Leppard was appointed Commander of the Order of the British Empire (CBE) in the 2016 Birthday Honours for services to policing and the prevention of economic crime.
Lepppard began his police in 1984 when he joined Surrey Police as a constable. He served as a traffic officer in the early years of his career. In 1989, he was promoted to sergeant and trained as a detective. As a senior investigating officer, he investigated a number of murders including the contract killing of Mario Commatteo. By 2003, he has risen to become the area commander of North West Surrey in the rank of chief superintendent.
In 2005, he transferred to Kent Police as an assistant chief constable with responsibly for specialist operations. In September 2005, he became assistant chief constable with responsibly for area operations. He led the investigation into the Securitas depot robbery that had occurred in February 2006. In December 2007, he was promoted to deputy chief constable. From March until July 2010, he was serving as temporary chief constable of the force.
In January 2011, he left Kent Police to join the City of London Police as Commissioner. In addition to leading the City's police, he was head of the National Fraud Intelligence Bureau. In the 2012 New Year Honours, he was awarded the Queen's Police Medal. He retired on 31 December 2015 and was succeeded by the force's Assistant Commissioner, Ian Dyson, QPM.
Leppard was appointed Commander of the Order of the British Empire (CBE) in the 2016 Birthday Honours for services to policing and the prevention of economic crime.
Adrian Leppard