In circumstances where the transmission system operator , other than for overriding reasons beyond its control , does not execute an investment , which , under the ten - year network development plan , was to be executed in the following three years , Member States shall ensure that the regulatory authority is required to take at least one of the following measures to ensure that the investment in question is made if such investment is still relevant on the basis of the most recent ten - year network development plan : ( a ) to require the transmission system operator to execute the investments in question