Even though Haddon is of a sturdy construction and has admirably withstood the test of time, restoration work on the Hall is an ongoing process largely made possible by income from visitors. The most noticeable recent repairs have been to the stonework of some of the windows made necessary by the long-term effect of weather, and corrosion of the wrought iron glazing bars. Following the restoration of three 15th Century windows in the Chapel, completed in 2004, work began on windows in the Long Gallery and Ante Room, overlooking the upper courtyard. This was completed in 2015.
This has been a delicate project with the intricate stonework being exactly copied, using local Derbyshire sandstone, in the same perpendicular style and carefully mortared back into position. The windows were carefully removed, and after assessment and taking a rubbing of each panel, each piece of glass was dismantled, gently cleaned, and then re-leaded. Some of the ancient, olive-green 'quarries' or diamond-shaped panels were less than a millimetre thick.
At present, members of the team are applying a UV filter to the inside of these new windows, to help protect the precious furniture and tapestries in the rooms.