Built on a basalt outcrop, the location was previously home to a fort of the native Britons known as Din Guarie and may have been the capital of the British kingdom of the region from the realm's foundation in c.420 until 547, the year of the first written reference to the castle.
In that year the citadel was captured by the Anglo-Saxon ruler Ida of Bernicia (Beornice) and became Ida's seat. It was briefly retaken by the Britons from his son Hussa during the war of 590 before being relieved later the same year.
His grandson Æðelfriþ passed it on to his wife Bebba, from whom the early name Bebanburgh was derived.
Vikings destroyed the original fortification in 993.
Normans built a new castle on the site, which forms the core of the present one. William II unsuccessfully besieged it in 1095 during a revolt supported by its owner, Robert de Mowbray, Earl of Northumbria. After Robert was captured, his wife continued the defence until coerced to surrender by the king's threat to blind her husband.
Bamburgh then became the property of the reigning English monarch and thus a Royal Castle. An important English outpost, the castle was the target of raids from Scotland. which is almost certainly why Henry II y built the keep.
The keep ia a massive square structure and the oldest surviving part of the castle. Its construction began in 1164 when a sum of £4 is recorded for its erection. Stones quarried three miles away at North Sunderland were carried to Bamburgh on the backs of horses. Built by scaffolding to the first storey, the rest of the Keep was built by masons using "over-hand" work. This means that i(internally) the walls overhang a little at each side as they are wider at the bottom than the top.
Built to withstand attack, the Keep's massive walls are between three and four metres thick. Its bottle- shaped doorway allowed soldiers on horseback to enter at a gallop without dismounting.
In 1464 during the Wars of the Roses, it became the first castle in England to be defeated by artillery, at the end of a nine-month siege by Richard Neville, 16th Earl of Warwick.
The Forster family of Northumberland provided the Crown with twelve successive governors of the castle for some 400 years until the Crown granted ownership to Sir John Forster. The family retained ownership until Sir William Forster (d. 1700) was posthumously declared bankrupt, and his estates, including the castle, were sold to Lord Crew, Bishop of Durham (husband of his sister Dorothy) under an Act of Parliament to settle the debts.
The castle deteriorated but was restored by various owners during the 18th and 19th centuries.
It was finally bought by the Victorian industrialist William Armstrong, who completed the restoration.
The castle's laundry rooms feature the Armstrong and Aviation Artefacts Museum, with exhibits about Victorian industrialist William Armstrong and Armstrong Whitworth, the manufacturing company he founded. Displays include engines, artillery and weaponry, and aviation artefacts from two world wars.
Since 1996, the Bamburgh Research Project has been investigating the archaeology and history of the Castle and Bamburgh area. The project has concentrated on the fortress site and the early medieval burial ground at the Bowl Hole, to the south of the castle.
Archaeological excavations were started in the 1960s by Dr Hope-Taylor, who discovered the gold plaque known as the Bamburgh Beast as well as the Bamburgh Sword.
The project runs a training dig for 10 weeks every summer for students to learn more about archaeological techniques and to further research into the Castle.