Today English is the main language employed for international communications in the fields of politics, commerce, science, transport etc. There were various possible time lines in history where this situation could have changed. If some other power like France or Germany had been successful in establishing their superiority on the European continent and building a larger empire, the French or the German could have taken its place. If Spain was successful in annexing Portugal and bringing all the Portuguese possessions in S.America, Africa and Asia under it, later powerful Spanish speaking countries could have risen in many places, enabling Spanish to become the most important language. If Islam had spread into more areas and become the foremost religion, Arabic would have been the world's main language. So, it was Britain's fortune in OTL that it could build the largest empire in history and make English lingua numero uno. OTL is the best conceivable time line for the English language.