On 10 July, in the May edition, the source explained (citation):

The Blue Book 2018 revisions, which began in January 1997, have affected the Index of production (IoP) and its components.
[...]
The published indices being re-referenced from 2015 equals 100 to 2016 equals 100

In response, we have revised existing series and updated their unit-descriptor metadata. Properties are otherwise unchanged.

The series reside in the historical catalog (United Kingdom » Industry » Industrial production » Detailed ONS Indicators) and include, for example:

• ONSK23JM.IGBR = Industrial Production: Manufacture of other basic metals and casting [24.4-5], (Ch. Vol. Index 2016=100, SA)
• ONSK26CQ.IGBR = Manufacture of basic metals [24], (Ch. Vol. Index 2016=100, NSA)
• ONSK279A.IGBR = Sewerage [37], (Ch. Vol. Index 2016=100)

Because catalog locations are subject to change, the upper-right search box on DataBuffet.com provides a "find in catalog" mode that accepts a mnemonic.

See also

• Data Revision: U.K. - National accounts - Re-referenced to 2016
• Data Revision: U.K. - Index of Services - Re-referenced to 2016
• Data Revision: U.K. - Household consumption - Re-referenced to 2016
• Data Revision: U.K. - GVA by industry (Q) - Re-referenced to 2016
• Data Revision: U.K. - Labor productivity - Re-referenced to 2016