Anyone who wants to study in an English speaking country has to take IELTS. Since the UK is an English speaking country, it is often perceived that taking IELTS is necessary to take admission in any of the universities of the UK. But you can study in the UK without submitting your IELTS score. Some universities give the opportunity to students to appear in interview rounds where their English is assessed. If their level and proficiency of English is found satisfactory then they are exempted from taking IELTS.
Also, if you have studied English as your major subject in your undergraduate or postgraduate, then you are exempted from taking IELTS. A lot of institutions in the UK also consider your grades in English during your high school. If your overall profile is found satisfactory and the institution thinks that the level of your English fluency is sustainable then you don't have to necessarily take the IELTS.
