WELCOME to Fairfax House as you’ve probably never seen it: in the middle of its winter deep clean.

York’s pre-eminent Georgian mansion closes every year at this time for five or six weeks so that it can be cleaned from top to bottom.

“We go through the whole house, assessing everything, cleaning everything, checking for any conservation work that is needed, dealing with woodworm,” says director Hannah Phillip. “Everything is done, from top to toe, with military precision, to make sure we don’t miss anything.”

This year’s deep clean is, if anything, more important than ever – because 2013 marks the house’s 250th birthday.

The John Carr-designed house was presented by Lord Fairfax, Viscount of Emley, to his daughter, Anne. And on April 19, 1763 – the Viscount’s birthday – he held a big party there to show the house off to the York society of the day. “They invited 200 people: it was one of the key events in the social calendar in 1763,” says Hannah.

Fairfax House will be holding a party of its own on April 19 this year to mark the 250th anniversary of that event.

But its 250th birthday celebrations will begin much sooner – from the moment the house reopens to the public on February 8, in fact.

That opening will coincide with the launch of Crowning Glory, the first of two major exhibitions at the house in its anniversary year.

“Crowning Glory will be an exhibition of Yorkshire’s historic jewellery and treasures,” says Hannah. As the title suggests, the exhibition will focus on headwear – tiaras, hair ornaments and coronets. There will be other stunning items of jewellery, however – including a stomacher brooch on loan from a North Yorkshire private collection that is similar to one known to have been owned by Anne Fairfax.

Sadly, the exhibition won’t feature any jewellery that belonged to Lord Fairfax or his daughter themselves. “We know they had a cache of diamonds, but we don’t know where they are now,” Hannah says.

Nevertheless, the exhibition will be a fitting celebration of the magnificent jewellery worn by members of the great Yorkshire houses in the Georgian era and at other times in history.

“It will be a very blingy exhibition,” Hannah says. “People will be wowed, and the female population of York will be smitten.”

• Fairfax House reopens after its winter clean on February 8. The Crowning Glory exhibition opens the same day.