Its early history is unclear, but it may have been founded in the 11th century on the site of a Roman fort overlooking a crossing of the River Lune.

The castle buildings are owned by the British sovereign as Duke of Lancaster; part of the structure is used to host sittings of the Crown Court.

Until 2011 the majority of the buildings were leased to the Ministry of Justice as HM Prison Lancaster, after which the castle was returned to the Duchy's management.

A new section of the café has been built, against the old outer curtain wall, which was reduced in height to afford views of the neighbouring Lancaster Priory.

Another renovated building adjoining the café is leased to Lancaster University as a campus in the city with small conference facilities.

[3] After the Norman Conquest in the second half of the 11th century, Lancaster was part of the Earldom of Northumbria; it was claimed by the kings of England and Scotland.

[4] As there are no contemporary documents recording the foundation of the castle, it is uncertain when and by whom it was started, but it is supposed that Roger de Poitou, the Norman lord in control of the Honour of Lancaster, was responsible.

If it was Roger who began construction, the structure would have been built of timber, probably incorporating the earthworks of the Roman fort into its defences.

[8] On the death of Henry II, the Honour passed to his son, Richard the Lionheart, who gave it to his brother, Prince John, in the hope of securing his loyalty.

Since the 12th century, the monarch appointed a sheriff to maintain the peace in Lancashire, a role usually filled by the duke and based at the castle.

[13] The Rolls show that John spent over £630 on digging a ditch outside Lancaster's south and west walls, and for the construction of "the King's lodgings".

[10] His successor, Henry III also spent large sums on Lancaster: £200 in 1243 and £250 in 1254 for work on the gatehouse and creating a stone curtain wall.

[16] A further devastation of the town, as had been inflicted in 1389, would have been an embarrassment for the new king; his expensive programme of building at the castle helped protect against this.

A small Parliamentarian force captured the castle in February 1643, established a garrison and set about building earthworks around the approaches to the town.

The outer defences fell in March; a siege of the castle lasted just two days as Parliamentarian reinforcements were heading to Lancaster from Preston.

The Royalists unsuccessfully tried to recapture Lancaster in April and again in June; the town and castle remained under Parliament's control until the end of the war.

[18] The instruction was not followed, and in August 1648 the town withstood a siege from the Royalist Duke of Hamilton who led an army south from Scotland.

King Charles was executed in January 1649 and shortly after Parliament again ordered the slighting of the castle, apart from buildings necessary for administration and use as a county gaol.

The monarchy was restored in 1660, and Charles II visited Lancaster on 12 August and released all the prisoners held in the castle.

Harrison had to divide his time between Lancaster and designing and building Chester Castle's Shire Hall and Courts; work at Lancaster slowed, partly because of dwindling funds due to war with France, and Harrison was released from the work as the Justices of the Peace felt it was taking too long.

The artist Robert Freebairn was paid £500 to paint twelve watercolours of the work in 1800 to be presented to the Duke of Lancaster, King George III.

[27] In 1802 the castle received more funding and Joseph Gandy was commissioned to complete the interiors of the Shire Hall and Crown Court.

This is partly because until 1835 Lancaster Castle was the only Assize Court in the entire county and covered rapidly growing industrial centres including Manchester and Liverpool.

[36] In the meantime, while access to the keep, towers, battlements and dungeons is currently denied to visitors, the castle operates limited guided tours seven days a week.

Ten tercet waymarkers, designed by Stephen Raw, each inscribed with a verse of a poem by Carol Ann Duffy have been installed along the route, with the tenth located here, to mark the end-point.

[41][42] This phase created a new teaching centre, as well as more than 5,000 sq ft of space, in which the Duchy has leased a section of the old kitchen to local coffee roasters and tea merchants, J. Atkinson & Co. (established 1837) to run a café.

It was instigated by King Henry IV, although legend attributes the work to John of Gaunt,[48] Duke of Lancaster from 1362 to his death in 1399.

[17] The sophistication of the gatehouse prompted John Champness, who wrote Lancaster Castle: A Brief History, to remark "it is perhaps the finest of its date and type in England".

[52] In his book The Historic Lands of England, Sir Bernard Burke suggests the wall may have been visible in more places 100 years prior to his writing in 1849.

[52] Letitia Elizabeth Landon's poetical illustration Lancaster Castle., to a picture by Thomas Allom showing the Shire Hall and the Priory, was published in Fisher's Drawing Room Scrap Book, 1837.