Aeilko Jans Zijlker [nl] acquired the original oil concession in Indonesia and the "Royal" imprimatur but died suddenly of a tropical disease in 1890.

Kessler had vast experience in the Dutch East Indies, having abandoned his studies at the Delft University at the age of 23 to seek his fortune there.

He had become partner in Tiedeman & Van Kerchem, an important business firm, but after financial difficulties in 1888 "returned broken and shattered in health to Europe, where he sought and found recovery".

[2] Kessler built the Royal Dutch almost from scratch, under very difficult circumstances: "an inclement climate, a hostile jungle and ineradicable lalang (sharp, tough grass), local crews difficult to manage, equipment that did not fit, tropical diseases, operational set-backs such as fires, and absence of adequate geological know-how", wrote J. Ph.

Due to his ability to quickly solve all kinds of technical problems and his incredible energy, he was accepted by his subordinates as "Toean Besor"—the Big Boss—not withstanding what many would describe as a difficult, high-strung personality.

With a small group of workers--"I demand the nearly impossible but there is no choice; everything rests on my shoulders"—Kessler again managed to turn things around and tripled oil production within a year.

Under Kessler, the company relaunched its principal product under the brand name "Crown Oil," expanded refining capacity, built a fleet of tankers and constructed several tank farms.

Gerretson, in his four-volume History of the Royal Dutch, heaped praise on Kessler, describing his leadership as necessary for the building of one of the world's major companies: "He was high-strung and passionate, forceful and impervious, a man of strong prepossessions and often difficult to get along with.

[8] Another book, Joost Jonker's and Jan Luiten van Zanden's A History of Royal Dutch Shell, lauds Kessler's "unbelievable capacity for hard work...Kessler's sometimes strained behavior emanated from the inner tension between his formal training as a gentleman and his leadership drive, from the necessity to sustain polite discussion whilst craving to go into action".

Kessler was a novice at oil and did not have much technical training, but "quickly developed a remarkable, intuitive grasp of the industry in all its aspects, founded on his keen sense for figures".

Kessler, according to Jonker and van Zanten, was "really Royal Dutch's founding father, the man who created the business and sustained it against the odds, perhaps even against economic common sense.

One of their sons, Jean Baptiste August "Guus" Kessler Jr., eventually became director-general of Royal Dutch Shell after Deterding resigned in 1936; he also played tennis for the Netherlands in the 1906 Olympics in Athens.