A few analysts were left scratching their heads following Persimmon's trading update on Monday.

The uncertainty surrounded its pre-tax profit forecast of £135m-ish for 2008.

According to FD Mike Killoran it was the market's consensus forecast (the average of several analysts' figures).

Not according to one City number-cruncher. "Most forecasts I am aware of were in the £155m-£170m bracket."

He reasoned that a few lower forecasts may have been thrown into the mix that were post-£40m of land writewdowns - a figure previously announced by the company.

The higher forecasts were pre-writedown and so any consensus figure would have been inadvertently skewed downwards.

Or was Persimmon slipping out some bad news while maintaining it was expected all along? he mused.

Others didn't think so and were unsurprised by the figure.

Meanwhile, another was left exasperated by it all. "The problem is that there's about ten consensus forecasts out there at any one time. You don't know which to believe and  a lot are out of date anyway."