European energy markets have undergone a major transformation as they have advanced towards market liberalisation and it is vital that the details of these developments be carefully examined. The success of liberalisation is based on smart regulation, which has been capable of providing solutions to unforeseen events in the process. Our paper seeks to contribute to existing understanding of the unexpected and collateral effects of the liberalisation process in the power system by examining a natural experiment that occurred in Spain in 2009. In that year, the electricity supply by distribution system operators disappeared. This change in retail market competition, as we demonstrate in this paper, has had an unexpected effect in terms of the system's balancing requirements. We undertake a rigorous assessment of the economic consequences of this policy change for the whole system, in terms of its impact on final electricity prices.