Scientist (The Man from MI.5)
A scientist gave the plans to a nuclear device to MI5 agent Captain Blacker, who was to rendezvous with fellow MI5 agents Tidman and Jimmy Bondson aboard Blacker's yacht, as cover for him to hand the plans over to Bondson.
After the plans were stolen and the yacht was blown up by Carl in January 1965, shortly before the rendezvous was to happen, Bondson contacted International Rescue for help. While explaining why he needed the help of International Rescue to Lady Penelope Creighton-Ward in the Forest of Digne, he explained how he was given the plans by a scientist living in a location he couldn't disclose for security reasons. Ultimately, International Rescue agreed to help, and the plans were recovered. (TV: The Man from MI.5)
Other sources dated the activities of International Rescue to the 1990s, (PROSE: The Dying Days) the 2060s, (PROSE: Titan Declares War! et al.) and the 2080s. (PROSE: Captain Scarlet in Death Crash! et al.)