Part of the Bank of England.

http://www.bankofengland.co.uk/pra/Pages/default.aspx

The Prudential Regulation Authority (PRA) is an agency of the Government of the United Kingdom, formed as one of the successors to the Financial Services Authority. On 1 April 2013 the PRA became responsible for the prudential regulation and supervision of banks, building societies, credit unions, insurers and major investment firms. In total the PRA regulates around 1,700 financial firms.

The PRA works alongside the Financial Conduct Authority (FCA) creating a "twin peaks" regulatory structure in the UK. The FCA is a separate institution and not part of the Bank of England. The FCA is responsible for promoting effective competition, ensuring that relevant markets function well, and for the conduct regulation of all financial services firms. This includes acting to prevent market abuse and ensuring that consumers get a fair deal from financial firms. The FCA operates the prudential regulation of those financial services firms not supervised by the PRA, such as asset managers and independent financial advisers.

PRA Supervisory Approach Documents

Financial service companies doing business in the UK.

http://en.wikipedia.org/wiki/Prudential_Regulatory_Authority_%28United_Kingdom%29