In all, the Land Registry reported 25,875 sales in the first month of the year, down from the more than 31,000 completed in each of November and December.
This total is also the lowest recorded since May, when just over 20,600 were reported.
The detached five bedroom house is located on The Vale, just off the Fulham Road, and is the second most expensive to be reported by Land Registry since it began releasing data in April.
The purchase was one of 530 residential sales in January in England and Wales for £1m or more – 322 of these were in London.
In contrast, the cheapest residential sale in January was a semi-detached property in Birmingham for £14,760.