Building 1000 was built in 2004 but initially failed to get tenants to occupy it. They were probably put off by the noise and pollution from the City Airport. After laying more or less empty for three years the Council decided it would be ideal for its new headquarters. Remember, this was before the financial crash and the ensuing recession. In theory it could have worked. The sale of over 50 sites would contribute to the asking price of £75million. (+£20million for retrofitting and moving). As a side note, 600 council jobs were lost because of the relocation.
They deal was signed in 2008 but unfortunately the Financial Crisis struck at the same time and property sales plummeted just at the time the Council were trying to sell its old buildings. That was just unfortunate timing.
If the council can make money by leasing its office space on their new asset, that seem to be a good option.
With hindsight they should not have bought the building, but they did and now have to make the best of a bad situation.