The world’s biggest iceberg – more than twice the size of Greater London – is on the move. After a few weeks loitering on the fringes of Antarctica, it’s begun to drift at pace once more.

A23a, as it’s known, broke away from the Antarctic coastline way back in 1986, but it’s only recently begun a big migration.

For more than 30 years, it was stuck rigidly in the bottom-muds of the Weddell Sea like a static “ice island”. A 350m-deep keel had anchored it in place.