For much of the post-WW II period until the late-1980s Britain was described as the ³sick man of Europe² suffering from a ³British Disease².  The symptoms of the ³disease² were low investment and low growth. An important component of this disease was fundamental to British institutions, namely Parliamentary sovereignty. This made it difficult for Britain to credibly commit to policies preferred by investors. Joining the European Economic Community, with its externally enforced constraints on policy-making, and the development of a cross-party economic ideological consensus allowed the UK to make more credible commitments to investors. The British Disease went into remission. The Brexit vote and related socio-demographic changes re-expose Parliamentary sovereignty¹s credible commitment problems. Is Britain headed for a relapse of the British Disease?