I thought it might be worth responding to the comment from Gerry. I don't get many comments and he raises a good point.

My first reaction is to say that I couldn't agree more that people should see homes as homes and not as investments. I also feel that if we had a better rented sector the obsession with investment in housing would be less.

That, however, is a debate for another day.

To the important question he raises: how can £1 trillion be wiped off the value of UK homes?

Here's my take.

For good or bad, like Faberge eggs, classic cars and underpants, houses have a value and that value is measured. Not by me, but by the Government and a host of other people. That value goes up, it goes down.

According to Nationwide houses will fetch, should you choose to sell, on average what they would have done in the May 2004.

The Government, when it did its books for 2004 (in this case when it put together the 2004 Blue Book), calculated the asset value of residential buildings in the UK to be £3,427 billion at the end of the year. This was up from £3,055 billion at the end 2003.

These are stated valuations put on the stock of residential buildings in the UK, not my estimates based on the 26 million homes and the average price given by Nationwide.

Had it done the sums for May 2004 it probably would have come up with a figure close to £3,200 billion.

When it did its sums for the value of residential buildings in the UK at the end of 2007 it came up with a figure of £4,313.6 billion. At that point prices were already beginning to slip and were down about 2% from peak.

So had the national accountants done the sum for the value of the nation's residential buildings at the peak of the housing boom in October 2007 they would come up with a figure of about £4,500 billion.

So on that basis the Government accountants and statisticians who deal with these number, and these are not generally the most excitable people, would tell you, me or anyone else who asked that from May 2004 to the peak of the boom the value of UK homes rose about £1.3 trillion.

They like me would probably hedge and say about £1 trillion.

But as a nation technically we were £1 trillion wealthier.

Now if the Nationwide figures are an accurate reflection of prices generally (and they would argue strongly that they are), we might reasonably expect - if the calculations were done today - a valuation put on the UK's residential buildings of much the same as in May 2004. That is a value more than £1 trillion less than at peak.

Stupid and silly as it may be, but rather like value being lost from the stock market - that is how "£1 trillion has been wiped off the value of UK homes".

Valuations may be nebulous things, but here is something to ponder on.

If my calculations are right, and I am sure someone will tell me if they are not, every UK taxpayer will end up paying on average about a fiver to Barratt as a tax rebate after it chose to revalue its land and work in progress.

In fairness to Barratt this is tax it has paid in the past, but that doesn't alter the fact that it will claim £142 million back from the revenue as a result of exceptional costs - that is exceptional costs based on the assessment that the value of the homes it expects to build on the land it owns is significantly less than previously assessed.

It is worth remembering these are not homes Barratt has actually sold.