Beverly Johnson thinks she has a “big mouth”. The 71-year-old star – who became the first black model to appear on the cover of American Vogue in 1974 – insists that she’ll never remain silent about her successes or her failures. Beverly told Vogue: “My scars and my mistakes and my learning process can be exposed in a way that’s not unapologetic, but also not sensationalised – because I’m too old to be sensationalised. “This is my story, it’s totally true – as my daughter would say, a little bit too true. And as my brothers and sisters say, ‘Can’t you keep anything to yourself?’” Beverly has l…