Excavations of Norwich Castle keep and mound will begin next week as details of a multi-million pound redesign have been unveiled.

Eastern Daily Press: An illustration of how the displays in the revamped Norwich Castle Keep could look. Pic: Haley Sharpe DesignAn illustration of how the displays in the revamped Norwich Castle Keep could look. Pic: Haley Sharpe Design (Image: Haley Sharpe Design)

Detailed plans for the £13.5m project to restore Norwich Castle to its medieval glory could be lodged by the end of April, and architects Fielden and Mawson presented some of their ideas to Norwich City Council on Thursday.

It includes a new 360 degree viewing platform on the battlements and more than doubling the visitor capacity of the keep from 180 to more than 500.

Preliminary excavation work will begin within days as archeologists explore the keep foundations and the man-made mound.

'Knowledge of the mound is very thin and we hope to learn a lot more, particularly if the keep has foundations and how deep they are,' said Hugh Fielden of Fielden and Mawson.

Eastern Daily Press: How the recreated Great Hall in Norwich Castle's Keep could look. Pic: Haley Sharpe DesignHow the recreated Great Hall in Norwich Castle's Keep could look. Pic: Haley Sharpe Design (Image: Haley Sharpe Design)

'They have got a year for excavations which start next week. That is a series of limited investigations in specific places. The most exciting thing we could find - and what we don't want to find - is a timber fortress.'

The architects said they have been studying some of Edward Boardman's drawings to piece together the original designs of the medieval keep, and plan to restore many of the elements from the 11th and 12th century.

'This is not just a castle, it is a royal palace,' added Mr Fielden. 'The vision is creating a new world class heritage offer in the heart of Norwich.

'This reflects the castle as having international significance in medieval Europe. A lot of background work has been done and we have been looking to the archives to find Edward Boardman's drawings a lot of people were not aware of before. We have been looking quite regularly to find out the original design.

'Norwich was the first castle in Europe to have an external stone staircase going up to the principal floor and we want to reposition that staircase.'

New entrances are planned for school and wedding parties, and the main entrance will be relocated

Mr Fiedlden added: 'The existing keep has a floor area of 1,160 square metres. We want to increase that by 250 to 300 square metres, increasing the whole by about 500 square metres. That allows us to go from 150 to 180 people in the keep to over 500. That is a significant improvement.

'We are recreating the principal medieval spaces but we are not intending a facsimile.'

Dr John Davies, chief curator at Norfolk Museums Service, said they hope to complete the project by Easter 2020.

'This is a really big project in financial terms,' he said. 'We have 92pc of the funding in place but it would be overambitious to stretch ourselves.

'Every generation has made its own contribution to the castle. We are not looking to disrespect other interventions and other architects have made their mark.

'The schedule is very tight. The castle will remain open and of course there are going to be major challenge in terms of logistics and construction work.'