The NPL did not have the expertise to build a machine like ACE, so they contacted Tommy Flowers at the General Post Office's (GPO) Dollis Hill Research Laboratory. Flowers, the designer of Colossus, the world's first programmable electronic computer, was committed elsewhere and was unable to take part in the project, although his team did build some mercury delay lines for ACE. The Telecommunications Research Establishment (TRE) was also approached for assistance, as was Maurice Wilkes at the University of Cambridge Mathematical Laboratory.