To be fair... I don't think they used pensions for leverage. I think the bank saved the pension funds by purchasing gilts (UK equivalent of US Treasuries) so as to stabilise the market. The pension funds were being forced to liquidate their holdings because the market was so unstable.
I think the hedge funds probably mounted an attack which forced the Bank of England to respond.
I am not thinking of 2008 as a comparison. For me, it's most like what would have happened to the US if it had adopted the Paul Ryan budget. It relies on phoney assumptions and a magic multiplier. All sorts of effects.
Paul Krugman compares this BOE intervention with Bagehot's Dictum, and thinks it made good sense as a lender of last resort thing. http://en.wikipedia.org/wiki/Lombard_Street:_A_Description_of_the_Money_Market#Lender_of_last_resort
Luckily, however, the big news today was that last quarter's GDP numbers were better than expected. So the UK economy is not as weak as either the government or the markets expected.