The royal seat of Cassiobury has been occupied by British kings, princes and warriors long before the Roman invasion in 55BC.

During Saxon times, Cassiobury became the seat of the Mercian kings. The Mercians were the most successful of the different groups of Anglo-Saxon peoples, with the Kingdom of Mercia dominating most of the south of England.

King Offa, the greatest and most powerful of the Mercian kings, later gave Cassiobury to the Abbey of St Albans to enlarge the revenue of the monastery. The manor then became the palatial residence of a succession of Abbots of St Albans for a period of about 900 years.

Cassiobury also stood as the seat of justice for the Hundred Courts, which were held 12 times a year. Their main function was the administration of law and the keeping of the peace.

The park is interceded by the River Gade and the Grand Junction Canal. There was also a trout stream and a mill referred to in the Domesday Survey of 1066.

The interior of the manor housed an eclectic collection gathered over the years by its various residents. Through the front door, guests entered a long and narrow entrance hall, the walls of which were adorned with valuable relics. One such artefact was the head of a Maori chief killed in New Zealand, which was brought over to England and presented to Lady Essex by Sir Capel in 1838 on his return from the East Indies.

The billiard room and card room had large stained glass windows and portraits of royals on the walls, including one of Henry IV, who laid the first stone of the house.

The manor had three libraries with a large collection of valuable books and some rare paintings.

An anteroom contained a small glass case which held a handkerchief used by Lord Coningsby to staunch a wound received by William III at the Battle of the Boyne. Above the case was a painting of the same event.

Also amongst Cassiobury’s collection was a ribbon of the Order of the Garter worn by King Charles I when he was beheaded during the English Civil War, following which the monarchy was briefly abolished and a republic called the Commonwealth of England declared.

In 1530, Henry VIII appointed commissioners to visit all the religious houses of the kingdom and take accounts of their possessions and ultimately to enforce their suppression and transfer their revenues to the crown. This was known as the Dissolution of the Monasteries.

The Abbot of St Albans appears to have refused to surrender his Abbey but died the succeeding year. Richard Boreman was appointed in his stead and, in 1539, delivered up the whole revenue of the monastery to the Royal Commissioners.

In 1546, Henry VIII granted the Manor of Cassio to Sir Richard Morrison in exchange for ‘knightly services rendered’. Morrison was a successful diplomatist in foreign service and a great favourite both with Henry and his son, Edward VI.

Shortly after Morrison took possession of Cassiobury, he commenced the erection of a large house. However, he fled the country before it was built to avoid the persecutions of Protestants by Mary I, and joined several distinguished noblemen on the Continent.

On his death two years later, the property passed on to his only son, Charles, who was knighted by Elizabeth I. Charles completed the rebuilding of the mansion commenced by his father and became sheriff of the county of Hertford. He also represented the borough of St Albans and Hertford in Parliament, and was later elected Member of Parliament for the county of Hertford. He continued to reside at Cassiobury until his death and was buried in the Essex Chapel in the Parish Church of Watford.

Charles’s only daughter and heiress, Elizabeth, married the brave but unfortunate Arthur, Lord Capel, who was beheaded for his fidelity to Charles I. By her marriage, Cassiobury became the property of the Capels, Earls of Essex, in whose possession it would remain for nearly 400 years.