MB 278 was constructed by J. White & Son on the Isle of Wight during the early months of World War I. Equipped with a steam engine, the naval pinnace was delivered to Harland & Wolff in Belfast in 1915 to serve her first mother ship, HMS Sir John Moore.

Following this, MB 278 was assigned to HMS Raglan, which was sunk off the coast of Imbros. The pinnace survived and, after five years stationed in Malta, joined the battleship Iron Duke in the Mediterranean. Subsequently, she served aboard HMS Barnham and later HMS Resolution in the Atlantic.

In 1929, MB 278 underwent her first major refit in Malta, during which she was fitted with a new 22hp Ferry engine. The following year, she joined the battleship HMS Queen Elizabeth. Just prior to the outbreak of World War II, she was assigned to HMS Erebus.

In March 1940, MB 278 was involved in an accident at Portsmouth dockyard, where she was crushed and sank, narrowly missing participation in the Dunkirk evacuation. Upon recovery, her hull was found to be badly damaged but was swiftly repaired, and she received a new engine. Evidence of her Dunkirk service remained visible in the form of a row of bullet holes caused by a German machine gun, which were apparent until her recent refit.

The Admiralty disposed of MB 278 in 1948, selling her to Thomas Duffy for £125. After Duffy's death in 1983, ownership passed to his son. The vessel was renamed Susan K. and underwent extensive restoration efforts. Despite the Admiralty’s original description of the vessel as a "round bilge ex-Naval hull of double-skin mahogany with mahogany shelter aft" in fair condition and without an engine, MB 278 is actually constructed of double-skin teak on rock elm and oak frames, with a third internal skin fitted athwartships. She features five steel bulkheads, and with proper maintenance, is expected to remain seaworthy for another century.

In early 2010, Susan K. was acquired by Michael Dennett, a boat builder based in Laleham, and was renamed MB 278. An extensive refit was undertaken, including installation of new engines, replacement of deck cabin sides, interior refurbishment, and replanking of the hull. Heather and Stephen Dennett, owners of Gay Venture, supported the restoration. Michael Dennett took MB 278 to Dunkirk in 2010 as part of the Dennett family’s Dunkirk fleet, maintaining her participation for five years and returning again in 2015.

Later in 2015, MB 278 was purchased as a gift for Pangbourne College. However, she was greatly missed at Dennett’s yard and has since returned to their care. MB 278 continues to be a regular presence alongside Gay Venture at numerous maritime events.