Six robbers posed as Muslim women in June and raided a Selfridges department store, stealing more than $2.3 million worth of watches.
Two of the robbers, Connor Groake and his half-brother Sam Curtin, fled the store, but their scooter spun out of control during their attempt to escape.
Curtin lay on the ground injured from the fall while Groake ran off, the London Evening Standard said.
Egyptian student Mohammed Hussein ran after Groake and pinned him down until the police arrived.
Judge Nicholas Price recommended Hussein receive an award for his actions.
Curtin and Groake pleaded guilty last week to conspiracy to rob and aggravated vehicle-taking. Curtin was sentenced to 13 years in jail while Groake received a sentence of eight years in jail.
The other members of the gang have not been arrested, the Standard said.