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/credit-risk-standardised-approach-ss

Related links

Benchmarking of Internal Approaches
PS11/20 - Credit risk: Probability of Default and Loss Given Default estimation https://www.bankofengland.co.uk/prudential-regulation/publication/2019/credit-risk-probability-of-default-and-loss-given-default-estimation