London's year-ahead house price expectations have deteriorated sharply, according to RBC Capital Markets, which described the shift as a warning sign in an otherwise flat market.
The net balance for the capital fell to -23% from -10% in a single month, a speed of change the bank called unusual.
RBC attributed the move to the concentration of tax-sensitive and sentiment-driven demand at the top end of the London market.
Continued deterioration could begin to drag more meaningfully on the national average, the bank said.
The assessment, from analysts Anthony Codling and Oliver Dyson, is based on the July survey from the Royal Institution of Chartered Surveyors (RICS), a monthly poll of estate agents and valuers that measures the balance of those reporting rises against falls.
RBC's overall verdict was that the market has stopped getting worse but has not started getting better.
New buyer enquiries were unchanged from June at -28%, having recovered from a March low of -41%, while agreed sales held at -30%.
The headline house price balance edged up to -30% from -32%, continuing a slow drift back from April's -35%.
Near-term sales expectations have improved for four consecutive months to -14%, and the twelve-month outlook nudged to +3%, the most positive reading since February.
Supply is tightening, with new vendor instructions recovering to -4% from -23%, which RBC said provides some floor under prices.
The July survey offered little comfort for listed housebuilders in the near term, with flatlining demand pointing to continued pressure on volumes.
More second-hand stock coming to market also reduces the urgency for buyers to commit to new builds.
Several builders told surveyors they were delaying new starts while working through existing inventory.
In the rental market, landlord instructions remained firmly negative at -27% as landlords continue to exit, a trend RBC linked partly to the Renters' Rights Act.
Tenant demand cooled sharply to -1% from +12%, yet rent expectations remained elevated at +28%.
