Increasing numbers of properties are being sold off-market.

After just one month, Henry Pryor’s new platform, NotOnTheMarket, has 277 subscribers, £76m worth of off-market property, and £108m of retained searches, with another £40m to be added next week.

Separately, data from The Buying Solution, the independent buying consultancy of Knight Frank, found that a quarter of London transactions between January 2010 and May 2016 were off-market.

Meanwhile, 44% of purchases agreed by The Buying Solution country team over the past financial year were for properties which had not yet been launched or were off-market, up from 37% during the previous 12 months and from 10% in 2013-14, across the whole range of property purchased.

Despite uncertainty ahead of the EU referendum and since the result, demand in both areas has been high, according to the research.

Although the ratio of active buyers per available property in prime London fell to 5.9 from 11.9 in the year to April 2016, underlying demand is strengthening.

Philip Eastwood, head of The Buying Solution in London, says the number of viewings increased 43% between January and May versus 2015 and competition remains strong for the best properties.

He said: “It is too early to see if demand returns following the EU referendum result. We are however now talking to a number of our clients who are seeing opportunities. Prices are already being reduced by 10% to counter higher transaction costs, so we are likely to see further reductions by motivated sellers.

“That is why buyers value the fact we can unearth off-market properties through our network of contacts.”

The number of viewings in the prime country market increased by 20% between January and May versus 2015 and new buyer enquiries are up 9% over the same period, according to Jonathan Bramwell, head of The Buying Solution in the country.

He said: “There will be opportunities for clients to negotiate some attractive deals at the £5m+ level of the market where, for once, there is a reasonable amount of supply. International buyers will also have the added advantage of being able to trade on a weak pound.

“We are optimistic about the coming months as we have motivated clients who still want to buy when the right opportunity becomes available.”