Question: HMS Wellington, is a "Grimsby"-class sloop, formerly of the Royal Navy, now moored alongside the Victoria Embankment, at Temple Pier, on which river that flows through southern England?
Context: HMS "Lowestoft" was a "Grimsby"-class sloop of the Royal Navy.  Built at Devonport Dockyard in the 1930s, "Lowestoft" was launched in 1934 and commissioned later that year.  She served on the China Station, based at Hong Kong until the outbreak of the Second World War.  "Lowestoft" served as a convoy escort during the war, both in the North Atlantic and off the west coast of Africa. City Cruises is a public limited company that operates scheduled public sightseeing cruises on the River Thames in London, serving Westminster, London Eye, Tower and Greenwich piers every day throughout the year.  It operates the services mainly using purpose-built wheelchair-accessible 'RiverLiner' vessels, which have a large open top deck and enclosed lower saloon with panoramic windows and bars, backed up by some ex-Paris single-deck conservatory-style sightseeing boats.  The company also owns a number of other boats with which it provides a variety of private charter and waterage services on the River Thames.  City Cruises owns the London Showboat brand, under which it operates an evening dinner, cabaret and dance cruise from Westminster Pier throughout the year, and also owns and operates the Restaurant Ship Hispaniola, which is permanently moored alongside Victoria Embankment close to Embankment Underground station in central London. HMS "Deptford" was a "Grimsby"-class sloop of the British Royal Navy.  Built at Chatham Dockyard in the 1930s, "Deptford" was launched in 1935 and commissioned later that year.  The ship saw early service on the Persian Gulf station, but the outbreak of the Second World War saw "Deptford" serving as a convoy escort in the North Atlantic and Mediterranean, sinking a German U-boat in 1941.  She survived the war, and was scrapped in 1948. The River Thames ( ) is a river that flows through southern England, most notably through London.  At 215 mi , it is the longest river entirely in England and the second longest in the United Kingdom, after the River Severn.  It also flows through Oxford (where it is called Isis), Reading, Henley-on-Thames and Windsor.  The lower reaches of the river are called the Tideway, derived from its long tidal reach up to Teddington Lock.  It rises at Thames Head in Gloucestershire, and flows into the North Sea via the Thames Estuary.  The Thames drains the whole of Greater London. HMS "Wellington (launched Devonport, 1934) is a "Grimsby"-class sloop, formerly of the Royal Navy.  During the Second World War, she served as a convoy escort ship in the North Atlantic.  She is now moored alongside the Victoria Embankment, at Temple Pier, on the River Thames in London, England, as the headquarters ship of the Honourable Company of Master Mariners, where she is known as HQS Wellington".  It was always the ambition of the founding members of the company to have a livery hall.  Up to the outbreak of war in 1939, various proposals were examined, including the purchase of a sailing ship, "Archibald Russell" . HMS "Fantome" was an "Cadmus"-class sloop launched in 1901, transferred to the Royal Australian Navy in 1914, returned to the Royal Navy in 1920, and sold in 1924.  She was the fourth ship of the Royal Navy to bear the name, which is from the French "fantôme", meaning "ghost". HMS "Hazard" was an 18-gun "Favorite"-class sloop of the Royal Navy.  She was one of four "Favorite"-class ship sloop s, which were a ship-rigged and lengthened version of the 1796 "Cruizer"-class brig-sloop .  All four ships of the class were ordered on 10 June 1823.  She was launched in 1837 from Portsmouth Dockyard. The "Bridgewater" class sloop was a class composed of two ships built for the Royal Navy, HMS "Bridgewater" and HMS "Sandwich" .  The ships were part of the Royal Navy's 1927 Build Programme as replacements for the "Flower"-class sloop . HMS "Penguin was an "Osprey"-class sloop.  Launched on 1876, "Penguin" was operated by the Royal Navy from 1877 to 1881, then from 1886 to 1889.  After being converted to a survey vessel, "Penguin" was recommissioned in 1890, and operated until 1908, when she was demasted and transferred to the Australian Commonwealth Naval Forces for use as a depot and training ship in Sydney Harbour.  After this force became the Royal Australian Navy, the sloop was commissioned as HMAS "Penguin in 1913.  "Penguin" remained in naval service until 1924, when she was sold off and converted into a floating crane.  The vessel survived until 1960, when she was broken up and burnt. HMS "Leith" was a "Grimsby"-class sloop of the Royal Navy that served in the Second World War.
Answer: River Thames