Is the world’s most important glacier on the brink of collapse?

It's been called the most important glacier in the world. The Thwaites glacier in Antarctica is the size of Florida, and contains enough water to raise sea levels by over half a metre. Over the past 30 years it has been melting at an increasing pace, and currently contributes 4% of annual global sea level rise. Ian Sample speaks to marine geophysicist Dr Rob Larter about a new research mission to the Thwaites glacier, the role of Boaty McBoatface and what it's like to see a region melt away before your eyes