An Adelaide Fringe artist’s lunchtime performance has turned violent after he was allegedly bashed with his own ukulele in a vicious attack.

The busker was in Rundle Mall, dressed as a pencil, when the incident occurred.

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Witnesses say bystanders stepped in after a passing man grabbed the busker’s instrument and began assaulting him just after 12pm.

They pounced on the alleged attacker, holding him down until police arrived.

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One person filmed the entire incident, which left the performer with head injuries.

A 29-year-old Clearview man is expected to be charged with assault and theft as well as drug possession.