A man found guilty of Australia's biggest art heist and accused of an unrelated Gold Coast robbery has handed himself in to NSW police.Brett Michael Williams, 47, was found guilty last year of stealing more than a dozen artworks from a northern NSW studio in 2004, including a painting that the owner claims is a Cezanne worth $100 million.He was due to appear in Southport Magistrates Court on the Gold Coast this week on an unrelated robbery charge, but failed to attend.Williams already was the subject of a warrant after twice failing to turn up for his sentencing over the art heist in Lismore District Court.A NSW police spokesman said today Williams voluntarily handed himself in to Lismore police on Wednesday.A jury found Williams guilty of the 2004 art heist after a short hearing in December last year.The Queensland charges included break, enter and steal, breaching bail and unlawful possession of a weapon.Queensland police allege Williams broke into the fashion boutique at the six-star Versace Palazzo hotel in March 2007 and made off with several clothing items.He was forced to leave the shop's safe behind after he was unable to push it through a hole he'd made in the ceiling, police allege.Details were being sought on Williams' next court appearance. AAP