At the time he joined Scott's Discovery expedition in 1901, he was a 33-year-old leading stoker in the Royal Navy, serving on HMS Duke of Wellington.

On this expedition, Lashly proved a success and was a member of Scott's "Farthest West" party exploring Victoria Land in 1903.

Before joining Scott's next Antarctic expedition in 1910, he served as an instructor at the Royal Naval College, Osborne, on the Isle of Wight.

Lashly then stayed with Evans in the tent to nurse him while Crean walked the remaining 35 miles (60 km) alone in 18 hours to reach Hut Point camp, where he was able to fetch help.

Upon his retirement in 1932, he returned to Hambledon where he lived in a house he called "Minna Bluff", after one of the landmarks on the road to the South Pole.