It has been argued that the tetragonal-to-orthorhombic structural transition found in all the parent phases of the Fe-pnictide superconductors is driven by frustration, and therefore frustration is a key ingredient of the superconducting state because the superconducting phases remain tetragonal. We will test this hypothesis by measuring the spin dynamics either side of the structural phase transition in the parent phase SrFe2As2. The objective is to search for changes in the spin dynamics on moving from the orthorhombic (unfrustrated) to the tetragonal (frustrated) phases. If frustration is important then a strong softening of the magnetic spectrum is predicted at certain points in the Brillouin Zone. The results will be interpreted with respect to a linear spin wave model which we have found successfully describes the magnetic spectrum at low temperatures.