Transocean Winner, a semi-submersible rig, was under tow by the tug ALP Forward from Norway to Malta when it encountered severe weather of the Hebridies. The effect of wind and wave on Transocean Winner hampered the tug's ability to control direction and speed. After 24 hours of being dragged backwards by the rig the towline parted and the tug was unable to re-attach the tow. Transocean Winnder eventually grounded on the Isle of Lewis.
The full report is available on the UK Marine Accident Investigation Branch website.