The importance of London to the UK's housing market cannot be understated.
For at least the last 30 years, the fortunes of the capital's housing market have affected what happens elsewhere in the UK, with events in London generally being felt by the rest of the country in subsequent months via a "ripple effect".
When house prices in London rise, those increases tend to be followed elsewhere, initially across the south-east of England and then beyond. Similarly, when the London housing market has caught a cold, the housing market elsewhere in the UK has subsequently done so.
The fortunes of few housebuilders are as closely tied to the London market as those of Berkeley Group, which is why its trading statements are so closely monitored not just by investors in the company - the fourth-largest of the quoted UK housebuilders behind Persimmon (Frankfurt: 882058 - news) , Taylor Wimpey (LSE: TW.L - news) and Barratt developments (Frankfurt: 859551 - news) - but also by housing analysts, estate agents and anyone with an interest in UK housing.
Today's update, which covers November, December, January and February, was something of a mixed bag.
On the plus side, so far as investors will be concerned, was the company's reassurance that it is "in a strong position and remains on target to meet its ambition to deliver at least £3.0bn of pre-tax profit over the five years ending 30 April 2021".
Almost as reassuring was Berkeley's assertion that "the housing market in London and the South East has now stabilised". That is why shares of Berkeley have risen by almost 6% today, taking the company's stock market valuation to just over £5bn.
It has certainly been a rocky ride in recent months. London's housing market, which has been supported by strong demand from foreign buyers during the last decade or so and especially at the top end, was rocked by the Brexit vote last June. Shares (Berlin: DI6.BE - news) of Berkeley Group traded as much as 38% lower following the poll and, despite today's rally, remain lower than they were prior to the EU referendum.
The after-effects of the Brexit vote were a drag for some months, as Berkeley noted today, observing that, in the seven months since the referendum, its underlying reservations were down 16% on the comparable period a year earlier.
It was not just the referendum, either, that hit the capital's housing market. George Osborne - named today as the new editor of London's Evening Standard newspaper - also contributed to that malaise when, in December 2014, he jacked up dramatically the rates of stamp duty payable on homes worth more than £937,000 as part of his overall reforms of the tax.
That hit the London market disproportionately and has resulted in a slowdown in transactions since, as Berkeley observes in today's statement. The company also cites another measure of Mr Osborne's, to reduce the extent to which buy-to-let landlords can deduct mortgage interest from their tax bills, as well as the extra stamp duty payable on buy-to-let property.
It has not only hit top-end properties, either, according to the company, which notes: "The reduction in reservations is across all price points."
Slightly offsetting these factors has been the fact that interest rates remain at ultra-low levels and the willingness of mortgage lenders to make credit available to homebuyers, while Berkeley also notes that there is still demand from foreign buyers, due to the collapse in the pound after the Brexit vote.
It you are buying in dollars, euros or even Russian roubles - the pound has fallen by more than 25% against the rouble since the referendum - a London property has not been this cheap for many years.
But exercising Berkeley Group most of all is what appears to be coming down the track.
Aside from Brexit uncertainty and recent changes to stamp duty, it also cites as a drag on the housing market the tough planning regime; extra costs from the Community Infrastructure Levy, an extra planning charge introduced in 2008; requirements from local authorities to build more affordable homes and Section 106, a clause in the Town & Country Planning Act that allows local authorities to place restrictions on how land can be used or impose obligations on developers in return for granting planning permission.
According to the company, this has led to housing starts in London falling by almost a third.
It adds: "Berkeley is concerned by this under-supply and the knock-on effect it has on the provision of housing of all tenures which, if not addressed, represents a threat to London remaining the inclusive and open global city which is so important to London and the UK's growth and prosperity."
Investors will be reassured by this trading update. Anyone who wants to see more homes being built in London, though, including the Government - which has made clear it believes housebuilders are to blame for the lack of progress - should be deeply concerned by what this influential and most impeccably-run of companies is saying.