With Utzon's departure from the project confirmed, Hall and his partners – Lionel Todd and David Littlemore as part of a consortium known as Hall, Todd and Littlemore – worked through the requirements to establish a new brief for Stage Three of construction, which included the task of constructing and designing the interior and foyer spaces. Hall had been under the impression he would be following Utzon's plans. It came as a shock to discover that the work required would be on a much larger scale.
Instead of the documentation they were expecting to find, all that Utzon had left were sketches and designs. There were no working drawings, nor were there the crucial drawings illustrating Utzon's most recent thinking available to them. All were missing, along with about 5000 sketches and drawings that had been placed in storage by Utzon's office assistant, Bill Wheatland, where they would remain, largely unseen, until 1972.
Hall spent the following months overseas visiting Utzon's consultants, including engineers Ove Arup and Jack Zunz, acousticians Cremer and Gabler, and Willem Jordan, with whom he collaborated on the halls. He also visited various concert halls in Japan, Europe and the United States.
A year after Utzon and his family departed Australia, Hall received a letter that would lead, over the following months, to Hall and others exploring the possibility of Utzon's return to collaborate with the government-appointed committee of architects.
Utzon insisted that Hall keep their conversations away from engineers Povl Ahm and Ove Arup, and friends and associates of Utzon. Hall noted that Utzon felt he could not trust Stan Haviland of the Sydney Opera House Executive Committee and that he was no friend of the Minister for Public Works, Davis Hughes, who had all but overtly engineered Utzon's departure from the project.
Nothing came of the backchannel discussions.
On 17 January 1967 the installation of the last (2,194th) precast shell segment effectively marked completion of Stage Two and work on the interiors could begin.