When HMS Challenger set off from Portsmouth to sail around the world in 1872 to make the first ocean soundings it was Queen Victoria’s equivalent of exploring Outer Space.

Now a photographic record of her four-year, 68,890 mile voyage has turned up in Dorset, and been auctioned for £20,000 to a private collector.

Challenger carried 249 miles of rope for sounding and recorded a record 26,850 foot depth in the Marianas Trench in the Pacific.