There are many ways in which one can improve their knowledge of the English language. From taking courses in a classroom scenario to learning through online tuition, there will no doubt be numerous ways to find that you can get better at English.
However, for those who truly want the best knowledge of the language and to be able to be understood by people all over the world, the most successful approach will be to take English courses in London.
By learning English in the country itself, you are far more likely to develop your grasp of the language in the most effective way, allowing you to speak as an English person actually does as opposed to how text books suggest that English people should. Furthermore, London English courses will leave you surrounded by people with English accents, meaning that you are likely to learn English with the right accent, and in turn that people both in England and even abroad will be far more likely to understand exactly what you are saying.
The rhythm of the English language can be surprisingly hard to get right as it can differ quite dramatically from many other language rhythms. As such, being surrounded by people speaking English will help ensure that this rhythm is far easier to adapt to as you learn the language.
From developing an accent that allows you to say English words in the correct way to actually simply picking up idioms and colloquialisms that English people will actually say, taking a course in English in the country itself will ensure that you have both the vocabulary and accent to be fully understood no matter where you go.