On 3 September 1878, it departed in the morning for a “Moonlight Trip”, transiting to Gravesend so that passengers could spend several pleasant hours touring Rosherville Gardens and other sights, and then returning to London in the moonlight after sunset. Princess Alice was behind schedule that night, fighting the tide.
It was to stop at the North Woolwich Pier, near the Royal Victoria Gardens and just downriver from the present-day Thames Barrier, to drop off some passengers. In accord with a common practice of the day, the master stayed in the slack water on the south side of the river for as long as possible while transiting Gallions Reach, just before arrival at the pier. Meanwhile, the much larger coal carrier SS Bywell Castle was proceeding downbound.
Observing the lights of the Princess Alice near the south shore of the river, the Bywell Castle set course for a starboard-to-starboard passing. Princess Alice altered course sharply to reach the pier, apparently not sighting the rapidly approaching Bywell Castle. The coal carrier rammed the passenger vessel amidships, splitting it in two.
The Princess Alice sank within four minutes.
Only one hour before, the twice-daily releases of 75 million imperial gallons of raw sewage from the sewer outfalls just upstream had occurred. Of the approximately 800 persons on board Princess Alice, over 650 died, either as a direct result of the impact or by drowning in the sewage-laden waters.
Public opinion blamed the Bywell Castle’s master for the casualty, even though he fully complied with the collision regulations and was exonerated by the subsequent official inquiry.
The master of the Princess Alice, who died in the casualty, was found to have violated the collision regulations. The Marine Police Force was made responsible to marine safety on the River Thames.
Shortly thereafter, London sewage was taken by barge and dumped at sea, rather than in the river. The incident remains to this day as the single greatest loss of life on the River Thames.