Inside a cosy cottage tucked away in the foliage-filled outskirts of Melbourne, Missy Higgins lets out a quiet sob. The celebrated artist has spent the morning wrangling her two children, Luna, six, and Samuel, nine, through the school gates before settling into the makeup chair on the set of her marie claire cover shoot. It is here – between a final coat of mascara and a thick cloud of hairspray – that the news breaks, bringing the crew and surrounding set to an abrupt standstill: Higgins’ long-awaited album, The Second Act, has hit the number one spot in the Australian charts, 20 years to the day since her debut album, The Sound of White, reached the same milestone. She’s fresh off the back of a sold-out national tour (which, due…