The FSA has blocked an undisclosed number of trades of undisclosed assets between banks and insurers.
The banks/insurers say these would help their liquidity, by lending/borrowing a relatively easy to trade portfolio of gilts or bonds, secured against a portfolio of other less-liquid assets.
The FSA says the resulting cross-holdings would make the financial system more unstable, and particularly that it would tie the insurance sector more closely to the banks.
http://www.ft.com/cms/s/0/0b93bb28-f7da-11e0-a419-00144feab49a.html