If the Works Information set down by the Employer is only a performance specification, who will do most of the design?

NEC3 and NEC4 Contracts
1

If the Works Information set down by the Employer is only a performance specification, who will do most of the design?

2

If the Works Information set down by the Employer is only a performance specification, most of the design will be done by the Contractor (effectively a design and build contract).