Nicholson was a professor of biochemistry at the University of Leeds in the United Kingdom. He started drawing metabolic charts back in 1955 and they gradually evolved into the works of art that you have seen in all the textbooks and on the walls of labs in offices in biochemistry departments around the world. I doubt that there's a single biochemist that hasn't studied these charts at some time during their undergraduate experience.
Lately his metabolic charts have been the property of the International Union of Biochemistry and Molecular Biology (IUBMB) but many of them have been marketed by Sigma-Aldrich [Metabolic Pathways].
Recent additions have included several minimaps of specific pathways such as those involved in lipid metabolism, glycolysis, the urea cycle etc. It's sad that we won't see any additions to this collection or any updates.