Lambert Smith Hampton advised Sunnyday Capital on the transaction.
The 11,754 sq ft offices at 40 Long Acre, WC2, are currently let to brand consultancy, Interbrand Group, with the lease expiring in June 2015.
TfL already owns the freehold of the offices and has acquired the long lease with 100 years left to run.
Property portfolio expansion
James McAdden, Associate Director of Central London Capital Markets at LSH, said: "We secured the sale of the offices following a highly competitive bidding process and the purchase price of £10m reflects the robust investor demand for West End office space."
Graeme Craig, Director of Commercial Development at TfL, said: "As one of the biggest landowners in London, TfL already has an extensive property portfolio. Acquiring the long lease to our site above Covent Garden Tube station is part of our new approach to investing in our properties to generate substantial long-term income that we can reinvest back into the transport network. Property is a key part of this strategy and we are actively exploring other opportunities to develop and expand our property portfolio."