For all the furore over rate-fixing at Barclays, no smoking gun has emerged to implicate ministers in the last government.

It seems there was regular contact between 'senior officials' - the former Cabinet Secretary, Sir Jeremy Heywood among them - about the inter-banking lending rate (Libor).

But did it go further than contact? Was there pressure to massage the figures? And were Government ministers in anyway involved?

MPs will be hoping that Paul Tucker, Deputy-Governor of the Bank of England, will shed some light on these awkward questions when he appears before the Treasury Select Committee this afternoon.

Back in the Autumn of 2008, the Bank of England and the Treasury were fire-fighting on many fronts.

If it turns out that they - or their political masters - overstepped the mark and actively encouraged Barclays to fix their rates , the political consequences would be huge.

But the emails released ahead of the committee hearing don't suggest that this was the case.

The pressure is on for MPs to do a better job in getting Mr Tucker to explain exactly what went on than they did when quizzing the outgoing Barclays boss, Bob Diamond.