The three main programmes of the Geneva-registered International Baccalaureate (IB) have grown substantially worldwide over the past decade, although the programmes have found a natural "home" in the United States. This paper charts the growth of the IB in the United Kingdom (UK) revealing that involvement there, mainly in England and mainly with the original pre-university Diploma Programme (IBDP), peaked at about 230 schools in 2010, but since then the IBDP has begun suddenly to decline. Yet, in no other country has there been a fall in IBDP provision. This paper offers some key explanations for this phenomenon, where a lack of funding and continued lack of university recognition in the face of Advanced Level (A-Level) reform and numerous "baccalaureate" developments has led to many state-funded schools in particular dropping the IBDP. Thirdly, this paper discusses a number of implications, both for the IB itself and education in the UK in general.