BLAENAU Gwent saw the biggest fall in house prices in England and Wales, new Land Registry figures show.
The average house price in Blaenau Gwent has plunged by 15.7% annually, to reach £61,860 typically.
House prices lifted by 5.6% annually in March to continue their growth at the fastest rate in nearly four years.
London property values are rising twice as quickly as the national average, with a 12.4% annual increase taking average prices in the capital to £414,490.
But prices across England and Wales also showed a "surprise" fall when compared with a month earlier, in what experts said is an indication that the market is not heading for a "runaway boom".
Average property values across the country now stand at £169,124, following a 0.4% month-on-month drop, which is only the second monthly decline seen over the last year.
The latest annual rate of increase follows a 5.2% year-on-year rise in February and marks the largest annual rise seen since August 2010.
In further signs that housing market activity is lifting, the latest figures from the Land Registry also show that house sales were around one third (34%) higher between October 2013 and January 2014 than they were a year earlier.
Some experts have cautioned that toughened mortgage lending rules which came into force this month could prompt a slowdown in the pace of the housing market recovery as the industry adjusts to the changes.
Under the Mortgage Market Review (MMR) changes, lenders have to ask people looking to buy a home or re-mortgage more detailed questions about their spending habits in order to check whether or not they can afford their mortgage repayments. They also have to apply a "stress test" to make sure these payments will still be affordable as and when interest rates eventually rise.
There have already been some signs that the housing market may be cooling off slightly. Property analyst Hometrack reported this week that there is evidence that buyers in London are becoming less willing to meet sellers' prices in the face of the recent strong hikes in house values seen in the capital.
Figures released by the British Bankers' Association last week showed that 45,933 mortgage approvals worth £7.5 billion were given the go-ahead in March, marking the lowest number seen since last November, although this figure is still 43% higher than in March 2013.
Matthew Pointon, a property economist at Capital Economics, said the Land Registry figures showing a "surprise" monthly fall in house prices provides "further evidence that, while the housing market recovery will continue, there is little sign it is turning into a runaway boom".
He continued: "That is not to say that the housing market is grinding to a halt. With the economy growing by a healthy 0.8% in the first quarter, and earnings finally rising faster than prices, demand for housing is not set to collapse."