Police dog Ernie has been hailed a hero after intervening in a gang fight.

The German Shepherd was on patrol when his handler spotted a youth on a moped acting suspiciously.

Seconds later the youth pulled a knife on a passer-by, who, in turn, also pulled a knife.

But Ernie was quickly deployed to diffuse the situation.

A police spokesman said: "We quickly joined in to backup our teammates and arrests flew for a collection of offences. A total of four knives were recovered along with a quantity of drugs. The moped was also seized."

Dozens of people have now taken to Facebook and Twitter to praise Ernie, who is a member of Merton Police K-9 unit.

One person said: "Big hug for Police Dog Ernie" while another said: "You are my hero of the day!"