On Tuesday 8th February between midnight and 02.30 the rig was engaged in skidding activities from slot 17 to slot 4 this required the rig to skid 16.3-metres from north to south, followed by 3-metres west. Skidding commenced around midnight.
After completing the skid south the rig was skidded to the west. At 02:30, after skidding 1.75-metres to the west, the upper section of the stairway of the SOUTH stairs between the skid deck and the drill floor fell to the skid deck.
The lower section of the stairway had contacted the bund around the well bay hatches (bund height 5.75 inches). As the rig continued to skid the lower staircase remained stationary, this resulted in the top of the lower staircase unhooking itself partially from the intermediate platform until the safety sling prevented further movement. As the rig continued to skid force was applied to the intermediate platform via the safety sling, resulting in the platform being bent.
The foot of the upper staircase which was resting on the intermediate platform was bent away sufficiently from its normal position, to allow the foot of the upper staircase to swing free. During this swinging action it unhooked itself from the landing at the drill floor level and fell to the skid deck. It struck a handrail and made contact with cables and cable tray before coming to rest on the skid deck. By the final position of the staircase it appears the staircase also twisted round laterally by 180-degrees prior to landing.