The Golgotha Project

 was a terrorist group formed during the 1960s, during the Cold War. It specialised in finding items considered "magical" for a collection. These included Excalibur and the secret object code-named "the Arimathea Artefact." This artefact was very dangerous. It opened a rift into another world. After the portal was closed with nuclear weapons, it was found the rift had formed a crater in the ground. The Project sought the Fourth Doctor, who travelled to the world, where they discovered the Second Doctor, whose companion Jamie accidentally began to destroy the world when he killed a Gallifreyan Woprat. All the people in the world were saved and the group was shut down. (PROSE: Heart of TARDIS)