What is the link between the European and the British Pharmacopoeia?

The texts and monographs of the European Pharmacopoeia are also an integral part of the British Pharmacopoeia. In addition, the British Pharmacopoeia provides for monographs for individual drug products and for a range of drug substances that are not the subject of the monographs in the Ph. Eur. When a monograph is adopted from the European Pharmacopoeia, it is marked in the BP by the European star circle next to the title.

[GMP Compliance Adviser, Chapter 14.K.5]