Plans for a “sunken” cafe and bar in the shadow of an ancient castle have raised fears among conservationists.

The ultra modern-designed licensed eatery is earmarked at a car park where the wall formed part of Rochester Castles’ original medieval gatehouse and is on a site steeped in centuries of history.

In the middle of a designated Ancient Monument Area, archaeologists have unearthed artefacts dating back to Roman and medieval times over the years.

In a report to Medway Council’s planning committee, expert Chris Butler said: “There is potential for any groundworks to damage or destroy nationally important archaeological remains.”

He said following numerous digs there was firm evidence of Roman, Saxon and medieval occupation.

In his heritage impact survey, he also felt the redevelopment of the land behind the former NatWest bank and now Chuck and Blades diner in the High Street would be detrimental to the surrounding period and listed properties.

But London-based Stolon Studio architects who have submitted a comprehensive report to the authority on the proposal do not agree.

Robert Barker from the architects, Stolon Studio, described the overall plan which includes upgrading the old three-storey bank building, number 40, and infilling a neighbouring vacant property, number 38 as a “modern reinvention” which “pays respect to history”.

The submerged cafeteria, referred to as The Pavilion, would have a green grass-effect roof to “mimic” the lawned castle embankment. It may also include a mini visitors centre.

A multi-part application has been submitted to excavate land for the redevelopment which is in the heart of the town’s conservation area.

The brief for the site at no 38 is to repair the gap in the high street with a new mixed-use infill building with flats on upper floors and commercial units across ground and basement levels.

At number 40, a three storey building with a two-storey annexe at the back, there are plans to convert the loft and extend the existing office use into the roof.

Stolon Studio which is acting as agent for the applicant, Kentish Asset Management, says in the report that the scheme “adds valuable, office, commercial and residential floor space” to the High Street.

Mr Butler’s in-depth report adds: “The construction of a new building at 38 High Street will involve groundworks, and the proposed pavilion building to the rear of the site is within the Rochester Castle Scheduled Ancient Monument.

“Deposits relating to the medieval and early post-medieval castle ditch have been identified in the rear of the site and there is a potential for any groundworks here to damage or destroy nationally important archaeological remains.”

Another issue likely to cause concern is the lack of a safe pedestrian route at the back of the site in Epaul Lane leading to Castle Hill.

Alan Moss from the City of Rochester Society, which has a say on planning issues in the town, said the application had been brought to members’ attention.

He said: “We have not come to an overall decision yet. But what I would say is that the design for number 38 seems rather bland compared to the ornate building next door.”

The group previously slammed an application for a fired chicken shop front in Rochester High Street as “garish” and out of sync with the town’s historic surroundings.

Chicken World, which is opposite Eastgate House, a grade 1 listed Elizabethan town house in Rochester High Street was blasted for its appearance by the City of Rochester Society who felt it was not in “harmony” with the period properties nearby.

A date has not yet been set for the sunken cafe application’s determination.