The Duke of Newcastle later built on a mansion on the site, but one of his successors would later avoid it as the Industrial Revolution left Nottingham sizeable slums. Instead, they rented the property out to tenants like Miss Kirkby.
In 1831, however, the mansion was targeted as part of the ‘reform riots’ launched in protest against the then current’s duke’s opposition to a change in voting rights.
The castle — which was been closed for the last three years to allow for the £30 million renovations — will re-open to the public on June 21 this year.
According to York Archaeological Trust head researcher Gareth Davies, the bones date back to sometime during the late 18th century.
‘At that time, the ducal palace had been converted to apartments and these bones were just found in a levelling layer of rubbish,’ he told BBC News.
‘We don’t know whether originally they were buried and then disturbed.’
The archaeological team were used to finding other types of animal bones at the site, Dr Davies noted.
However, he added, the monkey remains took the researchers by surprise.
Remains of another relatively exotic bird — European crane — were also found.
‘At some point people were keeping a menagerie, like a little zoo, in the grounds of the ducal palace when it was turned into apartments,’ Dr Davies told BBC News.
According to former Nottingham Castle volunteer Yvonne Armitage, the most likely former resident from that time to have kept exotic monkeys was one Jane Kirkby.
Dubbed its ‘most flamboyant’ tenant, Miss Kirkby lived in the castle between 1791–1825 — and was known for her hospitality, but demonised as ‘eccentric’ and ‘peculiar’ by the Nottingham press for being an independently wealthy, unmarried woman.
Her status and riches came from her grandfather, who was an illegitimate son of the Earl of Chesterfield, Ms Armitage told BBC News.
According to historical records, Miss Kirkby kept pets during her time in Nottingham Castle — among which were lap-dogs and a ‘large ape’ that, Ms Armitage said, served as Miss Kirkby’s ‘constant companion’.