This SS has not yet been added to the PRA Rulebook. It is available on the Bank of England website, here.

https://www.bankofengland.co.uk/prudential-regulation/publication/2013/market-risk-ss

Related links

Market Risk
PS23/20 - "Market risk: Calculation of risks not in value at risk, and stressed value at risk" https://www.bankofengland.co.uk/prudential-regulation/publication/2020/market-risk-rniv-svar