A moped gang nearly blinded a 75-year-old man after spraying him with a toxic chemical then snatching his expensive watch.
The robbers casually approached their victim on a busy high street before before spraying a noxious substance in his face.
The gang grabbed his wrist and stole the custom-made Cartier Pasha watch - a luxury model which can cost upwards of £3,000.
They then fled on a moped while paramedics rushed to the scene and treated the man for an eye injury.
No arrests have been made after the robbery, in Harrow, north London.