Civil servants are moving to Canary Wharf in a bid to save them from working in "ugly and expensive buildings".
The 5,700 employees from various departments are moving from Whitehall to 10 South Colonnade, a building owned by Canary Wharf Group. The relocation should be completed by the end of 2018.
The government is taking over a lease from Barclays that ends in 2032.
Barclays has agreed to hand over its lease interests in the site by the end of 2017. It said its employees in 10 South Colonnade will be moving to its other buildings in Canary Wharf, saving £35m annually.
Richard Archer, head of leasing and marketing at Canary Wharf Group, said:
We look forward to the arrival of the east London hub office at Canary Wharf which will continue the diversification and increase the number of people already working here.
Minister for the Cabinet Office, Ben Gummer, said: "This new hub will provide a better working environment for many London-based civil servants at considerably less cost to the taxpayer.
"We will be replicating this approach across the United Kingdom, putting right the historic mistake of forcing public servants to work in ugly and expensive buildings."