Which two vessels were involved in the 'Marchioness disaster' of 1989 on the Thames River in London?

The Marchioness disaster was a collision between two vessels on the River Thames in London in the early hours of 20 August 1989, which resulted in the deaths of 51 people. The pleasure steamer 'Marchioness' sank after being hit twice by the dredger 'Bowbelle' at about 1:46 am, between Cannon Street railway bridge and Southwark Bridge.

Both vessels were heading downstream, against the tide, 'Bowbelle' travelling faster than the smaller vessel. Although the exact paths taken by the ships, and the precise series of events and their locations, are unknown, the subsequent inquiry considered it likely that 'Bowbelle' struck 'Marchioness' from the rear, causing the latter to turn to port, where she was hit again, then pushed along, turning over and being pushed under 'Bowbelle's' bow. It took thirty seconds for Marchioness to sink; 24 bodies were found within the ship when it was raised.

An investigation by the Marine Accident Investigation Branch (MAIB) blamed a lack of lookouts, but their report was criticised by the families of the victims, as the MAIB had not interviewed anyone on 'Marchioness' or 'Bowbelle', but relied on police interviews. The government refused to hold an inquiry, despite pressure from the families. Douglas Henderson, the captain of 'Bowbelle', was charged with failing to have an effective lookout on the vessel, but two cases against him ended with a hung jury.