Here are the figures that the buy-to-let critics and cynics have been waiting for. Rents are plunging.

Okay, this is only one month's figures from the surveyors' body RICS, but the many buy-to-let critics will see these as heralding a transformation of buy-to-let bulls into buy-to-let rats ready to flee the market.

Certainly, if there is a surge in sales from the buy-to-let market this would increase downward pressure on house prices.

But while there are many noises made about and suggestions of a buy-to-let meltdown, any collapse in this market may prove less dramatic than many critics would like to see, unless there are changes in legislation reducing the long-term prospects.

There had been a surge in rents since the credit crunch bit last autumn. For my money there was always the suspicion that this was a temporary phase, as the market readjusted to former homeowners shifting to rental.

However, this period of growth in rents buoyed confidence in the buy-to-let market and certainly there appeared to be the whiff of smugness developing.

Now the market has settled a tad, the effects of broader economic trends appear to be showing through more clearly and the economic realities point to downward pressure on rents.

The bleak economic climate and shaky employment prospects will no doubt increase the numbers who shun high rents and push for cheap deals on a place to live. So demand in absolute terms is heading down.

While supply in broad terms is likely to head up, particularly when you add in the plethora of young professionals who bought two-bed flats (or should I say apartments) over recent years that are now looking to rent the second room to make ends meet.

So we can assume that rents will head south.

But the buy-to-let market has proven far from the simple to interpret and it may be that there will be no surge for the exit route despite the economics of the business changing so radically. That said, confidence in the market will take a beating from seeing falling rents.

The market will also be chastened by the much reported Standard & Poor view that as many as 40% of buy-to-let mortgages could slip into negative equity.

It is not easy to predict how the investors will react. Will they stick and hope to ride the downturn? Will they twist and cut their losses fearing worse may follow if they do not?

However painful the experience, I found it instructive to watch Location, Location, Location last night (well bits of it). It was interesting to see the fish-out-of-water that was Phil Spencer dealing with a falling market. He put in bids that he would describe as "reasonable in today's market" to have them rejected by the seller. That meant a 10% or more discount to asking price.

His unease when the seller rejected the bid in favour or renting was clear.

It is this trend that RICS suggests lies behind the plunge in rents.

To sell is to realise a loss, whether that is notional (against inflated expectations) or real in terms of hard cash. Emotionally that is to cross the Rubicon.

However irrational it may be, many buy-to-let investors may seek to ride out this downturn, even if it means ploughing in money to keep their micro businesses afloat.

The one thing that does seem to hold true at present is that in the current market it is unwise to take too much for granted.