Norwich Castle has been a part of Norfolk's life for 900 years, and now that connection is being celebrated in an evocative new exhibition. Trevor Heaton reports.

It was when she was writing one of the labels for her new exhibition on Norwich Castle that curator Paris Agar had that 'tingle' moment, a point when she realised just how much the building has meant to local people.

A small group of influential city folk, led by architect Edward Boardman and banker John Gurney, had refused to let the former county jail come tumbling down in the 1880s, and pressed for it to be a museum instead.

John was passionate about the plan, but had tragically been blinded in a riding accident. So when Boardman was drawing up his detailed plans in 1886 he made sure that his friend did not miss out. 'He sent him a sand plan [where his designs were 'built up' in 3D] so he could touch and 'see' them,' Paris said. 'We would think of doing that now – but back then? It was such a kind thing to do. It's so sweet.'

This is just one of the stories which you can discover in The Square Box on the Hill, which opens at the castle on Saturday February 10, and which chronicles nine centuries of this celebrated and Grade I-listed building, from its origins as a Norman royal palace to the much-loved museum of today.

Everyone has their own 'special castle memory'. Perhaps yours, like mine, was that shiver-down-the-spine moment at first seeing the Egyptian mummies. Or maybe visiting the dungeons, looking out over the old cattle market from the battlements, tracing your way along the paths that once wove round the mound – or a thousand other alternatives.

My love affair with Norwich Castle began, like many people's, with a school visit. It was doubly memorable because this was the first time – aged ten (!) - I had ever visited the city either.

I remember being overwhelmed by the building's sheer scale - so much grander than my home-town museum in King's Lynn. And then I caught sight of those enigmatic and long-dead 'residents', well…

It's impossible not to have a personal connection with this magnificent building, a true Norfolk landmark, for centuries the real seat of power in the county – and now one of the most important surviving Norman buildings in Western Europe.

The exhibition grew out of the vast archive which was gathered by the team behind the successful multi-million Gateway to Medieval England project, which will transform the keep and push the already-popular museum into the big league for England's tourist attractions.

Researching the bid meant uncovering hundreds of items about the castle's history from its vast archives. Many of these rediscovered gems had never been displayed before. 'It was in September 2015 when we opened up the Plan Chest at Shire Hall and took out the Boardman plans that we had that 'oh my God! Eureka!' moment,' Paris recalled.

'We thought: 'You know what? We could have an exhibition which would also be fantastic advocacy for the project.'

And that's what's happened. So as well as a fascinating time-journey through nine centuries of the castle's story, visitors will also have the chance to – literally – shape how the front entrance, café, shop and more will look. This information will be used in the next stage of the Heritage Lottery Fund project in June.

'The exhibition [which runs to June] will give us four months of feedback. This has always been a project for the people,' Paris explained. 'People have wanted to put back the medieval floor in the keep since the 1890s.'

The exhibition takes the visitor from its earliest days, when it became only England's third stone castle (after the Tower of London and Colchester), to its time as a royal palace, then centuries as the county jail. Evocative and often beautiful engravings and watercolours – many never seen in public before - will show how the castle fell on hard times in the 18th and early 19th centuries.

And people's stories are never far away, from the plaintive graffiti of unfortunate medieval prisoners to the hard-hitting comments of prison reformer John Howard. 'We've tried to bring in the human aspect wherever possible,' she added.

You can indulge in a bit of 'what if?' too, with three alternative designs for refurbishing the castle from an 1819 competition. We would have had a very different looking building if any of those had been accepted.

The many controversies about the castle are explored, including the 19th-century stripping and replacement of its deteriorating Norman facing stone. 'I'd imagine a lot of the original Caen stone is still in the city somewhere,' Paris added. 'It would make a fascinating project in itself.'

Other people wanted it to just crumble away, to be a romantic Gothic ruin. Let's be glad they didn't hold sway.

After centuries as a prison it finally opened as a museum in 1894, the ceremony being performed by the Duke and Duchess of York (the future King George V and Queen Mary). Hitler's bombs failed to destroy the castle, and there's a terrific Baedeker Blitz gouache which conjures up the spirit of those desperate days.

There will be plenty of chances to interact, from the 'what's that whiff?' exhibit in the prison section to 1860s stereograph photographs – 3D, Victorian style – and dressing up like a museum attendant.

Expect lots of quirkiness and nostalgia too, from the original revolving doors used from 1964 to 2000 – yes, you can go through them again – to the newly-conserved suit of samurai armour, one of the castle's best-loved exhibits, and a re-creation (in part) of the days when the castle had its own bar. Remember 'Castle Bitter'?

And you can add your memories and photographs of school and family visits in a social media archive that will grow and grow over the run of the exhibition.

Because, good folk of Norfolk, you are part of the castle's story too – and hopefully always will be.

The Square Box on the Hill, main sponsors Brown and Co, runs at Norwich Castle Museum from February 10 to June 3.