A Hackney police officer has been found guilty of assaulting a mentally ill prisoner who refused to pick up a piece of paper he had dropped on the floor.

Sgt Charles Pilbeam, 30, stamped on the 27-year old’s toes, pulled him by the ear and dragged him to the floor, saying: “Welcome to Hackney”.

The homeless victim, Abdi Ali-Ahmed, had “a difficult childhood” in war-torn Somalia and suffers from multiple mental health issues.

Pilbeam denied the charge, but was found guilty on Friday of two counts of common assault following a trial at Westminster Magistrates’ Court.

The incident, on March 2, 2013, occurred after the man had been searched under the Misuse of Drugs Act by other officers. He had not been arrested but was being served with a dispersal notice to leave Hackney, having voluntarily given up a small bag of cannabis.

One of the officers on duty at the time, PC Cordelle Sailsman, reported the assault to the Met’s Directorate of Professional Standards (DPS), which is responsible for investigating complaints against police officers.

Defence counsel Guy Ladenburg suggested Mr Ali-Ahmed was potentially violent, but during the trial PC Sailsman maintained he was “very compliant” and seated at all times.

Pilbeam admitted he had stood on Mr Ali-Ahmed’s foot for a period, “to stop him kicking out”, but said that the level of force was “next to nothing”.

DPS Deputy Assistant Commissioner Fiona Taylor said: “Sgt Pilbeam’s actions towards a vulnerable man are inexcusable and have no place in the Met.

“I commend the actions of the officer who had the strength of character and belief that if he reported this wrongdoing it would be dealt with appropriately.

“We must remember that MPS officers and staff engage with the public millions of times each year and the vast majority of those contacts are carried out with professionalism and courtesy.”

Pilbeam, of Stevenage, Hertfordshire, will be sentenced on August 7 at St Albans Crown Court.