During the Stanley regime, Castle Rushen with its garrison was the main centre of the Island’s administration and the most famous of them. James, the 7th, Earl of Derby, lived in it for a good while. The actual Derby House built within the curtain wall was constructed in the 16th century but it was heightened about 1643 at the time of the 7th Earl, only a few years before he was beheaded in the time of the Commonwealth in 1651.
The national archives of the Isle were preserved in two rooms of the Derby House, adjacent to the court room. The bigger of the rooms was dignified with the title of the Library and was used by the Clerk of the Rolls and his chief clerk. The civil records were placed here; those of the Diocese were kept at Bishopcourt or in the keeping of the Diocesan Registrar.
A curious discovery of old manuscripts was made in 1926, underneath the roof of the Derby House. A plumber in the course of his work found five old tea-boxes full of documents which had suffered from having been exposed to dripping water, some being in a state of pulp. They were found to be part of the records of the Rolls Office. Such as they are, they have given a select band of archivists some knowledge not met with elsewhere. They consist mostly of fragments, undated, of Setting Quest verdicts, some of the parchments showing 16th century script. An irritating example is the account of a verdict in the case of a defendant, a crofter, with the strange name ‘Aspallan’, resident under Slieau Whallian, near Tynwald Hill. This family name ‘Aspallan’ occurs only once in the Manorial Roll of 1515 and then entirely disappears except for this undated fragment.
(source: Island Heritage by William Cubbon (1952))