A forgotten staircase to a treadmill, the remains of a prisoner and a porpoise, and a 1970s pub are just a few of the finds recently unearthed (sometimes literally) at Norwich Castle.

As part of the Royal Palace Reborn project to restore the main castle keep to its Norman heyday, piles had to be driven into the ground. And when that ground has been continually inhabited for a thousand years, the layers of buildings, rubble, soil and stone have to be dealt with extremely carefully.

At the start of the project Norwich Castle’s senior curator of archaeology Tim Pestell was hoping to find evidence of some of the earliest buildings on the castle mound and expecting to uncover debris dropped or buried by the people who lived and worked here through at least 10 centuries.

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So, what have we learned about Norwich Castle?

Porpoise was eaten. The excavation unearthed lots of bones left over from medieval feasts, including a porpoise bone, alongside bones of rabbits, deer, cows, sheep, pigs and goats. “Porpoise was a high-status food,” said Tim. Rabbits were a specially-bred high-status delicacy too.”

One day soon we might be able to work out the medieval menus of particular feasts or even the diet during the 11th and 12th century sieges. Radiocarbon dating can determine dates to within a couple of years. “It might help us to put flesh on the bones, literally!” said Tim.

Our ancestors must have been nose-blind. Waste disposal was a bit, well, medieval and the lowest parts of the keep were thick with debris including broken pottery, burnt charcoal and food leftovers. “I think they were nose-blind!” said Tim.

The original mound was big – and quickly got a whole lot bigger. The first Norwich Castle, built for William the Conqueror, was made of wood on a circular mound heaped over a chalk promontory. Less than 30 years later this was massively enlarged for the stone castle built for the Conqueror’s sons, becoming England's largest man-made castle mound. The new castle was ready for a Henry I to enjoy Christmas in Norwich exactly 900 years ago in 1121.

Eastern Daily Press: How Norwich Castle would have looked in the 12th centuryHow Norwich Castle would have looked in the 12th century (Image: Nick Arber)

Eastern Daily Press: Tim Pestell, senior curator of archaeology at Norwich CastleTim Pestell, senior curator of archaeology at Norwich Castle (Image: Norfolk Museums Service)

The Normans didn’t always dig very deep foundations. The footings for the walls were only about a foot deep in some places.

Two hundred years after the first castle was built, a grand dining hall was built outside the keep. A big spread of flint was found which would have been the footings of Edward I’s new great hall.

A whole wall got lost. A very thick wall in one corner of the keep had been blocked off, probably when the castle was converted from a prison into a museum in the 1880s. The chapel was directly above so it is possible the huge wall was built to support an ornately vaulted chapel ceiling.

And a staircase was lost too. The castle was a prison for five centuries. It was remodelled several times and at one stage had a staircase leading to a treadmill room – where prisoners would work as punishment. The stairs were rediscovered in the current remodelling.

Eastern Daily Press: The prison cell block built within the Castle Keep in 1792 in a photograph taken in the late 1880sThe prison cell block built within the Castle Keep in 1792 in a photograph taken in the late 1880s (Image: Norfolk Museums Service)

Norwich had its own jailhouse blues. The colour-scheme on the staircase was revealed in traces of whitewash and blue paint on the hidden staircase, probably dating from the 1830s.

Not all archaeology involves digging deep into the past. The current revamp stripped back the old café area and revealed some remnants of how it looked when it was a bar in the 1970s. This space will be the new toilets. But the many fans of the castle café can rest easy as it will be relocated to a vantage-point site above the shop.

Eastern Daily Press: The 1970s bar at Norwich CastleThe 1970s bar at Norwich Castle (Image: Norfolk Museums Service)

We will get within touching distance of more of the Norman building. The ancient walls on the way to the new toilets will be exposed.

There’s less archaeology than might be expected beneath Norwich Castle. Because the castle has been extended and modified and repurposed so many times during its long history, much of the evidence of life in earlier centuries has been dug through and disposed of. There were excavation when the rotunda was built, on the footprint of part of the old prison, in the 1960s, but there is no record of any archaeological finds. “Everything had been shovelled out by the Victorians,” said Tim. The site had already been extensively excavated long before that too – during various stages of its centuries as a prison and when it was converted into a museum from 1888.

Less is sometimes more for archaeologists. “If I’m perfectly honest it’s a relief we haven’t found much as it means we are not destroying medieval architecture,” said Tim. “One of the things which stood out to me was how much had gone. We didn’t realise quite how much had been removed, particularly in the Victorian period. We want to utterly minimise how much we take away this time.”

Eastern Daily Press: The Royal Palace Reborn project is underway at Norwich CastleThe Royal Palace Reborn project is underway at Norwich Castle (Image: Norfolk Museums Service)

Buried archaeological treasure is not the same as buried actual treasure. What was Tim’s favourite find? “For me possibly the most interesting thing to come out of the project was two post holes in the south west corner,” he said. They were made before the stone keep was built but after the mound was finished. If the line extends to three posts then it will be evidence of a structure. “It could be from the 1060s but we are probably looking at 1080-90, an early Norman house,” said Tim.

Just one skeleton was unearthed – probably a prisoner. That grave was a surprise but there are a number of known graves of prisoners who were executed at the castle. Those hanged after 1830 were buried on the castle mound in graves marked with their initials and date of death.

Eastern Daily Press: Grave marker for double murderer James Blomfield Rush who was hanged and buried at Norwich Castle for killing Isaac Jermy and his son, of Stanfield Hall, near WymondhamGrave marker for double murderer James Blomfield Rush who was hanged and buried at Norwich Castle for killing Isaac Jermy and his son, of Stanfield Hall, near Wymondham (Image: Norfolk Museums Service)

There is still lots to learn. “We are still learning an awful lot about the prison,” said Tim. “The octagon shape of the rotunda matches the 1830s governor’s house. The governor is the all-seeing eye at the centre of the prison, surrounded by exercise yards.”

There might have been some wonky weaving at the castle. One of the items uncovered was a piece of bone used to pack down threads on a medieval loom. It had been polished smooth by contact with the wool, and until the owner could replace the possibly dropped pin beater, fabric might not have been quite so tightly woven.

When the transformation is complete in the spring of 2023 the Castle Keep will look like a Norman royal palace once again.

The restoration of one of the most elaborate castles in Europe will colour in its magnificent past and show off some of its finest features.

The project, supported by the National Lottery Heritage Fund, is reinstating medieval floors and rooms and creating a new visitor entrance, café and shop.

Norwich Castle was built as a palace as well as a fortress and is an exquisite example of the very grandest of Norman architecture.

Some parts of the building will be open to the public for the first time, others will look completely different as time is rewound and floors replaced, doorways reopened and museum artefacts redisplayed to tell the story of the castle, Norwich and Norfolk.

Nationally important medieval treasures will go on show in a new gallery in partnership with the British Museum and high on the battlements a new fully accessible walkway will give panoramic views across the city, with digital reconstructions of the medieval view, allowing visitors to compare past and present.

Norwich Castle remains open while the keep is being transformed.