As one of the great landmark buildings of Norwich, the castle is an instantly recognisable symbol of the city. It still looks and feels like a castle, raised upon a city centre mound with its keep rising above the Castle Mall complex

And, despite its numerous uses over the centuries and, of course, the 19th-century equivalent of stone-cladding that gives it a shiny smooth exterior, it is still a magnificent and sturdy structure - as dominant as it was when Henry I sat down for his Christmas lunch there in 1121, not long after work was finished on it.

From royal palace to a squalid jail and then a museum, the structure has played a pivotal role in the history and façade of Norwich over the ages, since the Norman demolished the best of 100 Saxon homes to make way for those first earthworks that saw it rise above the medieval city.

From the 14th century the keep was used as the county gaol, before the prison moved to Mousehold Heath, and was then transformed by renowned architect Edward Boardman in 1894 into the museum it is today.

There have been further changes over the years, including an upgrade in 2001 to ensure the building and its contents remained accessible and relevant to a modern audience.

It is a county treasure per se, yet the Norwich Museum and Art Gallery also hosts great treasures too – from Iceni torques of the Snettisham Hoard and Roman artefacts to Egyptian relics, works of art by John Crome and John Sell Cotman from the Norwich school and Ted Ellis' dioramas.

In fact, it has everything from battlements to butterfly collections. Everyone who ever went to school in Norwich – not me by the way – seems to have a memory of the castle and the museum and now take their offspring back regularly to admire the artefacts and attractions.

The mighty keep, for all its sinister history, is a focal point, with its galleries and garderobes, deep wells and excavations.

The ongoing popularity of the castle and museum in vividly illustrated by the latest attendance figures with a record-breaking 214,726 visitors in the year 2014/15. Underpinning that are the imaginative exhibitions that have been staged such as Roman Empire: Power & People, The Wonder of Birds, and Homage to Manet.

But now there is a £12m plan to transform the Keep and turn Norwich Castle into East Anglia's number one tourist attraction.

It is possible to achieve that: the location, the treasures within and the appetite is there, and hopes of a link with the British Museum to further strengthen that.

In fact, there can be few stronger endorsements of what Norwich Castle has to offer than the British Museum seeking to create its first gallery outside London in the castle. As Dr Robin Hanley, head of operations and learning at Norfolk Museums Service, said, that would see the 'long-term loan of nationally important medieval collections' and judging by the success of the Roman and Birds exhibitions, there is huge demand for high calibre exhibitions in Norfolk.

Norwich Castle is one of the finest attractions of Norfolk – of East Anglia – already, and with this drive to attract a further 100,000 visitors, it will give the city further national and international renown.

Some £1m of government money has already been made available for archaeological and structural surveys of the castle to provide evidence in support of a £9m Heritage Lottery Grant bid, money that must be spent wisely and deliver meaningful results.

What is crucial is that it retains its character as Norwich Castle.

Those who live and work in Norfolk, and admire it and the treasures within, have an important part to play.

Consultation events on the proposals are due to take place over the summer, and it will be interesting to see more detail emerge of the plans.

But there are two groups whose views will be priceless: those who do not currently visit the castle (what do they think and what would encourage them to set foot within) and, significantly, younger visitors.

What is particularly admirable is engagement with a younger audience – asking young people to record their ideas for the castle in a video booth.

They, like their parents a generation before, will have had at least part of their childhood memory shaped by a visit to Norwich Castle, and it is fitting they should have the opportunity to shape that for future young people.

This is a golden opportunity to see the city's architectural treasure have a hold for another generation.

The £9m Heritage Lottery Grant application is crucial to that, but those in charge of our museum services should not stop there but should also seek additional European funding to seize this opportunity to make Norwich Castle a museum of international standing.

This is a priceless opportunity; a chance too valuable to miss out on.