JUST like the city’s famous buses, you can wait decades for a castle to be found in Glasgow and then along come two at once.

In what is being described as the most significant archaeological discovery in the city in many years, a Scottish Water project has uncovered the site of the legendary Partick Castle, a building that was lost centuries ago and which many people doubted even existed.

Archaeological fieldwork to the west of the River Kelvin on the north bank of the Clyde has revealed the medieval remains of Partick Castle and another castle-like structure built over the original fortification.

GUARD Archaeology found two structures, one from the 12th or 13th century, which they say was likely to be the base of a bishop’s castle. Documentary evidence show that charters indicating its existence were signed in Partick in medieval times, but there was no proof of where the building stood until the recent dig.

The second ruin is believed to be the Partick Castle that was built in 1611 for George Hutcheson, a wealthy Glasgow merchant and benefactor whose generosity led to the foundation of Hutchesons’ Grammar School.

The lands of Partick were given to Glasgow Cathedral in 1136 by King David. It was believed to have subsequently become the country seat of the Bishops of Glasgow, with a fortified stone structure of some kind likely erected on the site – building documents relating to the construction by George Hutcheson of a tower house in 1611 specify the demolition of a pre-existing structure.

Conversely this later tower house became known locally as the “Bishop’s Palace”. The ruin of this 17th century building stood on the west bank of the River Kelvin, near the position of the railway bridge until it was removed around 1837.

According to GUARD, prior to the work commencing, their archaeologists little suspected they might encounter such significant archaeological remains.

Although historical evidence strongly suggested there was a royal estate at Partick when nearby Govan on the opposite south of the Clyde was a medieval ecclesiastical centre, and which later became a seat of the Bishop of Glasgow, previous evaluations and testing by other archaeological companies had drawn a blank. These examinations had apparently shown that the overall site had been heavily disturbed by industrial works during the 19th century, and it was assumed there was only a very slim chance of any remains of the mediaeval castle of Partick surviving.

GUARD explained: “It was not known whether one area of slightly higher ground in the west of the site was a result of underlying archaeological remains or whether it was artificially raised during the clearing of later industrial buildings; this spot became the focus of our attention.”

Experts discovered a series of archaeological features including ditches, a well, several stone walls, significant amounts of pottery, metalwork, leather, glass and animal bones, all dating from the period between the 12th or 13th century to the 17th century.

GUARD Archaeologist Beth Spence, who is leading the excavation, said: “This fits with the historical references to the original bishop’s residence being erected no earlier than the 12th century and demolished in the early 17th century prior to a new tower house being constructed.

“So the archaeology we are encountering is probably the remains of both of these residences and what we will need to do once we have completed our excavation is disentangle the remains of the later tower house from the earlier castle.”

GUARD project manager, Warren Bailie, said: “These findings are of national significance and provide a rare glimpse into the medieval beginnings of Partick and Glasgow.

“The survival of these medieval remains is especially remarkable given that the site, not unlike many industrial river banks across Britain, has witnessed such large-scale destructive development over the centuries.

“However, this recent wave of development has seen Scottish Water work closely with GUARD Archaeology and West of Scotland Archaeology Service to ensure that this important site is afforded the ethical approach it deserves.”

Any areas where these significant medieval remains cannot be preserved in situ will be fully excavated and any subsequent research and specialist analyses on the assemblages will be published in due course.

Scottish Water environmental advisor Simon Brassey said: “As part of the project planning, Scottish Water identified the possibility of archaeology and so factored in time for the area to be pre-excavated.

“However, the discoveries are much more exciting than we had expected and we are delighted that we have been able to uncover something of such importance.”

Hugh McBrien, of West of Scotland Archaeology Service, said: “There was documentary evidence that the bishops of Glasgow spent time in Partick.

“It has been known there was a tower house or castle in the 17th century but all we had were antiquarian drawings and documents.”