For more than three decades, visitors to London’s Natural History Museum have been greeted by the sight of a skeletal diplodocus dinosaur – affectionately known as Dippy – but in 2015 the curators made the bold decision to replace the replica bones with the very real skeleton of a blue whale.

This Horizon documentary follows the painstaking two-year-long process of dismantling Dippy – who will be going on a tour of public spaces across the UK next year – and hanging the yet-to-be-named whale from the girders of the museum’s entrance hall for its unveiling this summer.

The film also tells the fascinating story of the whale’s discovery after it beached on the shores of Ireland in 1881.