From 20 March, the extensive art collection, which to date has simply adorned the walls of the family stately home, is to be opened up in its entirety to the public for the first time.

William Parente, grandson of the seventh Duke of Portland, said his family had taken a decision 15 years ago that this priceless art should no longer be locked away.

“We’d been very private for 50 years and we wanted to open things up. We knew there was this fantastic collection, I’d grown up with it, and we all felt a bit uncomfortable that we were the only ones who saw it,” said Parente.

He said it had been “crucial” that the artwork, of the sort rarely seen outside large London galleries, remained in the local area. By making the public gallery – funded by an endowment from the family – a permanent home for priceless works such as the Michelangelo sketch and five Van Dyck paintings, Parente said he hoped this small corner of Nottingham could grow into a cultural hub.

“Keeping the art in Nottinghamshire was the most important part of this project for us,” he said. “This was once a rich mining area that suffered terribly from the closing of the pits, and still hasn’t recovered. We’ve had the thick end of 30 years of misery, so we were desperate to contribute in any way we could to get things moving and we were keen to use the art as part of this.”