He added that a colleague had pointed to a similarity between the tower's design and one of Wren's early ideas for St Paul's. He said: "This throws a completely new light on our design."
Foster stressed the tower's environmental credentials. He said: "It has a much narrower base than a conventional building. The form allows air to flow around it, which reduces energy use and makes it a fresher building for those inside."
The agent for the block, John Forrester of DTZ, said he was confident that he would attract tenants. He said: "It's a long time since there's been a great commercial building in London."
6 Skanska project director Gary Clifford said work on the plaza at the rear of the building and snagging work on the interior of the tower would be completed by the end of June.