When vessels are in narrow channels or close to each other they are effected by forces called "interaction"(each other) and "ground effects". Although the River Pate is very wide the channel is very narrow as the river is shallow. When the Royston Grange met the Tien Che these forces caused them to collide. The Tien Che was a tanker which had been partially unloaded down strem so that she could get up the river. She had not been freed of the residual gas that remains after un-loading and there was a massive flash over which killed all aboard the Royston Grange, which was down wind. Some crew members from the tanker survived. The enquiry found that the Master of the Royston was going too fast, (but not that of the tanker). The Royston was a Liner, i.e. she ran to B.A. regularly on a schedule. Many crew members had "friends" in B.A. who used to cross the river on the ship before she left for ports further north. They usually returned on the ferry from Montevideo. The total number lost was 99. Vale.