Why British Phantoms used Spey engines

Did British Phantoms need reheated Rolls-Royce Spey engines to operate from Royal Navy carriers?

Yes, and the domestic engine also protected the program by connecting it to British jobs and industrial policy.

Reheated Rolls-Royce Speys supplied the performance considered necessary for British Phantoms to operate from Royal Navy carriers. British engine content also connected the purchase to domestic employment and industry. That political support could make a procurement program harder to cancel. The wider argument credits the Royal Navy with using this approach effectively between the wars, losing much of that skill after 1945, and gradually recovering it from about 2005. Operational requirements and industrial politics could therefore reinforce support for the same purchase.