We are fortunate that so much of the interior decoration has survived in Powerscourt House, Dublin designed in the first half of the 1770s by Robert Mack for Richard Wingfield, third Viscount Powerscourt. The interior of the house has rightly been called ‘schizophrenic’ by Christine Casey owing to a rich and eclectic style derived from a number of hands. The stair hall was decorated by James McCullagh assisted by Michael Reynolds and for work here and in a number of other rooms in the building his bill ran to over £730. An exuberant mélange of arabesque scrolls, urns, acanthus leaves, palms and portrait medallions, the stair hall is one of the city’s most madcap pieces of ornamentation. Unfortunately it is also one of the most difficult to examine, being excessively cluttered with signage and retail bric-a-brac…