At 8 PM on Thursday February 1996, the massive single-hulled tanker Sea Empress is about to enter the Cleddau Estuary at Milford Haven, against a receding tide.
Onboard it carried a cargo of some 130,000 tonnes of valuable North Sea crude oil.
The ship had just been boarded by a local pilot, whose job it was to guide the ship into a deep channel between the treacherous rocks that guard the entrance to the Haven.

At 8:05 they encountered a second tidal current running across the mouth of the estuary, pushing the vessel onto a new course - straight for the mid-channel buoy.
The pilot called for an immediate 5 degrees to port - but it was too little, too late. The Sea Empress just missed the buoy, but at 8:07 the crew felt the vessel judder. The mid-channel rocks prized open the starboard tanks like a can opener. From below the decks came the sound of rushing water, and the unmistakeable stench of oil.