Northwood Investors has exchanged contracts to buy Templar House at 81-87 High Holborn, WC1, from private investor Michael Feldman.
The US private equity firm, set up by former Blackstone Real Estate president John Kukral, is paying £55m for the 100,544 sq ft freehold.
The price reflects a yield in the region of 5.75%.
Northwood is expected to examine options for a long-term redevelopment of the building.
EDF Energy rents the entire 91,857 sq ft of office space and is expected to exercise an option to renew its lease in July next year until January 2019.
It pays £3.2m a year, equating to £34.84 per sq ft overall and sublets the space to Metronet Rail.
The retail space is let to five tenants at a total rent of £376,750 pa.
It is the second major London asset sold by Feldman this year, following his disposal of 1 Poultry, EC2, to Perella Weinberg Partners in March.
Northwood invests on behalf of a number of US state pension funds.
It completed its debut London deal in 2012 with the acquisition of 90 Long Acre, WC2.
BNP Paribas Real Estate advised Feldman; Northwood was unrepresented.
Jack.Sidders@estatesgazette.com