Following the poser I posted on that rather surprising spike in planning times for residential schemes, I have had a few questions and a few suggestions.

The pint for the first (and sensible) response going to Alasdair Reisner, Head of Industry Affairs at the Civil Engineering Contractors Association.

But by way of an answer to Noble's comment today and to a few other emails quizzing me on what I think may lie behind that paradoxical spike in the apparent time taken to process residential planning applications.

I'll be putting a fuller set of thoughts and analysis in a piece I will be writing for the Housing Market Intelligence report and, to a lesser extent, in an article for Barbour ABI out at the end of this month. But here's a brief run through of what notions the data appears to be supporting.

As I hinted there appears to be a combination of reasons. And having looked at the data in a number of different ways the strongest set of explanations appears to be this:

Firstly, there was a drop in applications coming through and it would seem that this disproportionately impacted on smaller schemes. Why spend time and money putting in an pretty non-contentious scheme into planning if you can't see yourself building it out for a few years, by which time you might want to build something else?

Secondly, there appears to have been less pressure from housebuilders to see their schemes pushed through. Indeed, as Alasdair Reisner emailed me to say, there were suggestions that housebuilders were actually sabotaging applications to avoid triggering option payments.

And as he added, if you've sacked a load of your planners who's left to answer queries and follow up your applications - a very good point.

Certainly on the street there were plenty of joking comments about housebuilders eager not to win approvals. And the data on withdrawals does seem to support this suggestion.

These factors appear to have kickstarted the spike. But what seems to have pushed it higher later on was that, with time freed up, the planning authorities moved on to tackle their backlog of older schemes.

Add into the mix of approved schemes a bucket load of projects that have been around for a number of months and it really does distort the figures, particularly when the numbers of quicker-to-address schemes is running at low levels.

The peak of the spike does seem to correspond to a leap in the number longer-to-approve schemes within the overall mix of projects approved.

And it does seem that once the backlog was reduced and fewer longstanding projects were there to be dealt with the spike came down.

Obviously, I am still looking for other suggestions.

What I certainly found interesting looking at the data from a range of angles was the sensitivity of the measure of months to approval when you calculate it from the date of approval.