Portland Works was awarded Grade II listed status by English Heritage in 1995 and subsequently upgraded to Grade II* listed status in 2007 following an updated survey of Sheffield’s historic metal trades sites. Grade II* is the second highest listed status awarded by English Heritage and only 5.5 per cent of all listed buildings have attained this level of protection (2.5 per cent of listed buildings have been awarded Grade I status, i.e., Windsor Castle, Buckingham Palace, etc.).
Grade II* listed status not only recognises that a building is of regional importance, it also indicates that it is of ‘more than special interest’ nationally. English Heritage summarised the importance of Portland Works in its 2007 listing upgrade description as follows:
“Portland Works is a large integrated cutlery works built in the 1870s. The complex is an extremely good and complete example of a large purpose-built integrated cutlery works dating largely from a single 1870s building phase with a well designed layout for this building type. The works was mechanised, with evidence for a steam engine, but there are also unpowered workshop ranges, illustrating the fact that Sheffield based its reputation upon the supremacy of traditional methods; it was said in 1879 that `the highest excellence can be attained only by the employment of intelligent hand labour’.
This type of complex is very distinctive to the industrial identity of Sheffield, which, at this time was known throughout the world as a centre of excellence in the manufacturing and processing of steel. Portland Works is an important survival which demonstrates the layout of such a complex, highlights the limited use of power in the cutlery manufacturing process, and retains both hand forges and steam grinding rooms, extremely rare survivals of building types related to specific processes, with probably fewer than five sites in Sheffield now retaining evidence of both. These characteristics, together with the degree of completeness of survival make this site of particular importance and justify its upgrading to Grade II*.”
English Heritage – Listed Buildings Online (http://lbonline.english-heritage.org.uk)