On the river Lek, passing Nieuwegein, Netherlands.
Built in 1944/45 in Glasgow for the Royal Navy as a Landing Craft Gun (Medium) in short LCG(M), 100 built.
Details as warship: http://www.navypedia.org/ships/uk/brit_aws_lcgm1.htm
Details as river cruise vessel: http://www.debinnenvaart.nl/schip_detail/7771/
The MS Sir Winston is now a mid-sized river cruise ship that can carry a maximum of 68 passengers.