Cathay A333 at Sydney on May 16th 2014, could not retract landing gear

A Cathay Pacific Airbus A330-300, registration B-LAH performing flight CX-100 from Sydney,NS (Australia) to Hong Kong (China), departed Sydney's runway 34L but could not retract the landing gear. The aircraft levelled off at 5000 feet with all gear still down and entered a hold, the crew worked the related checklists and consulted with dispatch however without success. The aircraft returned to Sydney for a safe landing on runway 34L about 35 minutes after departure.