Today we get the what could possibly be the most pre-spun British budget ever, though don’t rule out the traditional “rabbit from the hat” surprise so beloved of British finance ministers.

The important stuff for the markets is that with ratings agencies still threatening to rob Britain of its AAA status, it will be pretty much fiscally neutral – i.e. no serious economic stimulus on offer – borrowing will have come in  a little lower than expected this year and the government’s independent forecasting body will predict the economy will eke out just enough growth this year to avoid a new recession.

In other words, don’t expect much market reaction, though the fact the slightly lower borrowing may allow slightly lower debt issuance in the coming year could give gilts a small fillip.

With precious little in the coffers this will be a deeply political budget, balancing the twin needs of a centre-right/centre-left coalition, despite U.S. Treasury Secretary Geithner’s warning this week about the futility of austerity for austerity’s sake.

So what does a chancellor of the exchequer do with little or nothing to spend?
In economic terms, he tinkers. That is not to say that tinkering might not be politically explosive.