[2] He left maritime life after the attack on the SS Sagaing at Trincomalee in 1942, during which his wife Jessie and his son Duncan were killed.
On 27 January 1971, Robertson departed from Falmouth, Cornwall, on board the Lucette, a 43-foot (13 m) wooden schooner built in 1922 which the family had purchased in Malta with their life's savings.
On 15 June 1972, Lucette was holed by a pod of orcas and sank approximately 200 miles west of the Galapagos Islands.
By their 38th day as castaways, they had stored dried meat and fresh water in such quantities that they intended to begin rowing that night to speed their progress.
Robertson, who had been keeping a journal in case they were rescued, recounted the ordeal in the 1973 book Survive the Savage Sea, on which the 1991 film of the same name was based.