To make sure that your written content is as accessible as possible, it should be written using simple language and in plain British English. You can also think of it as ‘writing the way you would talk’.
This means that users will all equally be able to access and understand your content when they might have different levels of knowledge or language proficiency (for example, if English is not their first language).
You can read about this writing style with examples at the dedicated page of the University’s Editorial Style Guide.