Charles Herbert Lightoller, born in March 1874, began his maritime career as an apprentice on a sailing barque in Liverpool at the age of fourteen. In 1889, he experienced a shipwreck in the Indian Ocean. Lightoller later served as Second Officer on the RMS Titanic during its ill-fated voyage in 1912. After the ship sank, he survived by reaching a raft and was eventually rescued by the RMS Carpathia.

During World War I, Lightoller was awarded the Distinguished Service Cross (DSC) for his efforts in hunting German U-boats, including ramming and sinking one of them.

In 1929, Lightoller's wife, Sylvia, discovered the hull of an old steam pinnace lying in the mud at Conyer Creek, eight miles east of the River Medway. They were searching for a vessel to convert into a cruising yacht. After a survey confirmed the hull was sound, they proceeded with the conversion, rigging the vessel as a ketch with jib, mainsail, mizzen, and mizzen staysail. The yacht was named Sundowner, an Australian term for a tramp, reflecting Sylvia's Australian heritage.

Sundowner was launched on 28 June 1930. Following trials on the Thames, she undertook her maiden voyage to France. Over the next decade, the yacht cruised extensively along the northern coast of Europe, reaching as far as the Baltic Sea, navigating the Somme River, and traversing French canals. During this period, she participated successfully in numerous international competitions.

In 1932, the vessel's robust hull and rigging were tested during a force ten storm off Ostend. Despite the severe conditions, Lightoller's seamanship ensured their survival through 32 hours at sea, covering a distance that would normally take eight hours.

As tensions escalated in Europe in 1939, Lightoller was selected for a secret mission to survey the European coast in an area reminiscent of the setting of The Riddle of the Sands. On 30 May 1940, the Admiralty announced the requisition of Sundowner for the Dunkirk evacuation. Lightoller insisted that if the vessel was to be taken, he would command her alongside his eldest son, Roger, and a Sea Scout named Gerald Ashcroft.

On 1 June 1940, Sundowner crossed the English Channel with five other ships. En route, they rescued the crew of the motor cruiser Westerly, which was broken down and on fire, returning them to Dunkirk. Coincidentally, Lightoller's second son, Trevor, had been evacuated from Dunkirk 48 hours earlier.

Sundowner embarked 130 men, tightly packed aboard. During the return journey, the crew employed skilled evasive maneuvers to avoid enemy aircraft. The vessel, heavily laden and riding low in the water, faced the risk of being swamped by the wash from fast-moving destroyers. Upon arrival at Ramsgate, the disembarkation of troops nearly caused the vessel to capsize until Roger Lightoller instructed the men to lie down and remain still.

Although the Lightollers were eager to return to Dunkirk, only vessels capable of 20 knots were permitted to continue. Sundowner subsequently served as a coastal patrol vessel, participating in several notable rescues, including the recovery of a Walrus flying boat crew after a sea crash and assisting following a Spitfire belly-landing in the Thames Estuary mud.

The yacht also featured in a newsreel documentary, demonstrating the role of similar vessels in coastal defense and rescue operations.

In June 1946, Charles Lightoller regained possession of Sundowner. By July 1947, the yacht returned to Dunkirk to participate in the Pavilion d'Or event. Charles Lightoller passed away in 1952 at the age of 78. His wife Sylvia continued to sail Sundowner, competing in numerous events. At age 80, she helmed the yacht and led the Armada of Little Ships during the 25th Anniversary return to Dunkirk, until a fall forced her to be flown back to England, ending her active association with the vessel.

Under new ownership, Sundowner voyaged to Spain and the Mediterranean, returning ten years later. In 1986, the yacht sustained damage to her steering and planking after being struck by a northeast gale, the remnants of Hurricane Charlie, off the North Foreland in Kent. Later that year, the East Kent Maritime Trust assumed stewardship of the vessel.

As of May 2012, Sundowner was owned by The Steam Museum Trust, which also manages the Ramsgate Maritime Museum. In July 2020, the yacht was purchased by a new owner with plans for a complete restoration.