Roth and Semple also worked together setting up and running the London Geometry Seminar which operated for 40 years and provided one of the major focal points for geometry research throughout the world. Semple also worked with Du Val who joined the London Geometry Seminar but they only wrote one joint paper.
Roth at Semple din nagtrabaho nang sama-sama-set up at pagpapatakbo ng London geometry pantas-aral na ginagamit para sa 40 taon at ibinigay ang isa sa mga pangunahing focal points para sa geometry pananaliksik sa buong mundo. Manggagawa sa Semple din Du Val na sumali sa London geometry pantas-aral ngunit sila lamang wrote isang pinagsamang papel.