This paper offers a novel interpretation of the 1890 British Ultimatum, by bringing to the front of the stage its techno-diplomatic dimension, often invisible in the canonical diplomatic and military narratives. Furthermore, we use an unconventional historical source to grasp the British-Portuguese imperial conflict over the African hinterland via the building of railways: the cartoons of the politically committed and polyvalent Portuguese artist and journalist Rafael Bordalo Pinheiro (1846-1905), published in his journal Ponto nos iis, from the end of 1889 and throughout 1890. We argue that the Ponto nos iis cartoons played a so far overlooked role in the unfolding of British-Portuguese affairs, as they shaped at a distance a diplomatic exchange with the British satirical journal Punch. Attacking and counterattacking his fellow cartoonists in Britain, Pinheiro surged into the role of informal diplomat. This cartoon visual and public diplomacy unfolded in the pages of both journals and was tied to the two countries' colonial conquests in Africa, where the Portuguese and British empires were competing to dominate the African hinterland through large technological systems. Hence the cartoons made visible to wider audiences the otherwise hidden role that technologies played in the two countries' affairs. In turn, the cartoons aimed at persuading the Portuguese public and ruling classes alike that only regime change, from monarchic to republican, would restore the wounded Portuguese national pride.