The earliest known written record for the town of Odiham, which sits to the east of Basingstoke, appears in the Domesday Book of 1086. One of its most well-known landmarks is Odiham Castle.

Known locally as King John’s Castle, Odiham Castle was one of just three fortresses built by King John during his 17 year reign, from 1199 to 1216. The castle was built on 20 acres of land acquired from a local lord and was an ideal location, situated halfway between key royal residences in Winchester and Windsor. It took seven years to complete at a cost of over £1000 - approximately £1.5million today. When it was first built, Odiham had a two-storey stone keep, square moat, raised banking and palisades.

It was from Odiham Castle that King John departed in 1215 to meet his rebel barons at Runnymede in Berkshire. The agreement that came from this meeting formed the basis for the Magna Carta, one of the most important documents in world history and which established the principle that everyone – including kings - is subject to the law. However, King John did not uphold the terms of the charter and, just a year later in 1216, the castle was besieged by the French Dauphin, later King Louis VIII, in support of the barons during the First Barons’ War.

King John died in October 1216 and Odiham passed to his son, Henry III. Henry gave the castle to his sister Eleanor in 1236 and it became the de Montfort family home when she married Simon de Montfort in 1238. In 1263, de Montfort rebelled against Henry and was killed by the king’s forces at the Battle of Evesham in 1265; Eleanor was exiled and Odiham Castle was returned to the ownership of the Crown.

During the 14th century, the castle played a role in several significant events, including the sitting of Parliament, a rebellion led by the powerful Despenser family and the imprisonment of King David II of Scotland. The Scottish king was imprisoned in England for 11 years after his capture at the Battle of Neville’s Cross in 1346, part of this time was spent at Odiham Castle. He was held under a light guard and was allowed to keep a household. In 1357, his release was agreed in exchange for a promised ransom by the Scottish nobility – the ransom proved too high for the nobles to pay but David remained free.

By the 15th century, Odiham Castle was used solely as a hunting lodge. The castle fell into disuse at the beginning of the 1600s, to the point that as early as 1605, it was described as a ruin - which it remains to this day. In 1792, the Basingstoke Canal was built through the southern corner of the bailey adjacent to the castle ruins.

Archaeological excavations were carried out by Hampshire County Council Museum Services at Odiham Castle between 1981 and 1985. The finds from these excavations are now in the care of Hampshire Cultural Trust.

The ruined keep was restored in 2007 by Hampshire County Council with guidance from English Heritage. Today, Odiham Castle is open to visitors all year round.