A giant ice block more than twice the size of Greater London is on the move, years after its formation.

The world’s biggest iceberg is on the move after more than 30 years being stuck to the ocean floor. The iceberg, called A23a, split from the Antarctic coastline in 1986. But it swiftly grounded in the Weddell Sea, becoming, essentially, an ice island. At almost 4,000 sq km (1,500 sq miles) in area, it’s more than twice the size of Greater London.