The RJ85 aircraft was being prepared for a charter flight from Perth Airport to Granny Smith, Australia. During the pre-flight checks, the flight crew did not identify that there was no pressure in the braking system and did not pressurise this system prior to engine start. Around the time of the start of the final engine in the starting sequence, the aircraft began to roll forward. The dispatcher noticed the aircraft rolling and alerted the crew. The crew attempted to use their foot brakes and the park-brake, however, there was no brake pressure. Around 18 seconds after the aircraft started to roll, it collided with movable aircraft stairs, which were in front of the Cobham terminal. The stairs struck the front of the aircraft, beneath the right pilot seat. Shortly after, NJW collided with a bollard in front of a light pole, then with the light pole itself. Findings – The crew did not effectively check the brake system pressure during either the originating checklist or the starting checklist. As a result, the crew did not identify that there was no brake pressure prior to engine start. – After engine start, the aircraft inadvertently rolled forward and collided with objects at the edge of the apron. The absence of brake pressure, the slope of the apron and the absence of a nose-wheel chock were contributory to the aircraft rolling forward. – The operator’s dispatch practices did not involve placing chocks on the nose-wheel for engine start. Although some ground handling procedures indicated nose-wheel chocks should be used, the operator’s training did not involve a step to place chocks on aircraft nose-wheels. The absence of a nose-wheel chock fore of the aircraft reduced the defences against the aircraft rolling forward. – The crew had a very limited opportunity to take corrective action before the aircraft collided with objects at the edge of the apron. It is likely that the short distance to the edge of the apron and the influence of surprise combined to reduce the crew’s ability to respond.