Before his father left Japan, Alexander was engaged by the British representative Harry Parkes as a student interpreter because of his fluency in Japanese.

Alexander assisted British consul Edward St. John Neale during the Anglo-Satsuma War and was based on the flagship HMS Euryalus (1853) during the conflict.

He later accompanied the European task force during the Bombardment of Shimonoseki and the negotiations for opening the port of Hyogo to foreign settlement and trade in 1864.

However, the new Meiji government found use for his talents, and he was sent to London and subsequently to Frankfurt to make arrangements for Japanese students in those countries and to hire foreign advisors in all areas of expertise to come to Japan.

On the death of his mother in 1877, he returned to the Netherlands on six months leave, but was ordered to visit the Exposition Universelle and to assist in commercial negotiations in Berlin.