The sale of property valued at £10m plus increased by half in the year following the European Union referendum, a Freedom of Information request revealed.
Specialist lender Octane Capital requested the information from HM Revenue and Customs, showing 300 £10m plus properties were sold in 2017 - an increase of 100 from the previous year.
An Octane Capital spokesperson said the data suggests Brexit uncertainty made property price tags at the highest end of the market significantly more attractive for buyers.
A third of the homes valued at £10m plus and sold in 2017 were bought by second homeowners - this demographic was also increasingly active in purchases of property valued at £2m plus, with the number of second homeowners buying within this budget growing from 800 in 2016 to 1,900 in 2017.
Jonathan Samuels, chief executive of Octane Capital, said: "The mainstream property market saw transaction levels tail off considerably following the EU referendum vote, but at the very top end of the market activity levels soared as ultra-wealthy opportunist buyers cashed in on rapidly softening prices.
"The weakness of sterling means a fair percentage of these buyers were almost certainly based overseas, as some of Britain's wealthiest cities became a goldmine for foreign investors seeking a bargain."
Mr Samuels said he believes the fall in the pound "more than compensated" for the 3 per cent stamp duty surcharge on additional properties.
Mark Harris, chief executive of mortgage broker SPF Private Clients, said: "The top end of the property market is very thin at the best of times with a limited number of transactions.
"No doubt tax and political uncertainty act as a deterrent, but the majority of transactions will have been sales to overseas investors benefiting hugely from the weak currency."