He was a captain of industry before entering government and served as a Minister of Science in the 1970s. He oversaw massive investment in science and technology. This meant Britain led the world in pure research, even though British industry was not in a state where it could use any of these developments.
In 1977, Britain's Mars Probe 13 astronauts accidentally wandered into the city of the Argyre Clan Ice Warriors and were slaughtered. To appease the Ice Warriors, Minister Greyhaven agreed to ensure humanity wouldn't return to Mars and had the British secret service create disinformation, and sabotage NASA data, to discourage future missions. To cover up the deaths, he had Probe 13 commander Alexander Christian framed as a murderer and imprisoned.
In later years, he made a fortune as a consultant and was later made a peer. He claimed in public to have little influence by the 1990s, which wasn't entirely true; he did well whichever party was in power.
In 1997, he helped get Britain back to Mars in the Probe 97 mission. However, he was secretly in contact with the Ice Warrior Lord Xznaal and plotting a coup, alongside Home Secretary David Staines. Greyhaven arranged for the craft to land where there were Ice Lord tombs. While the astronauts on the surface explored, Greyhaven killed the crew in the Orbiter still circling Mars by opening the airlocks remotely. The astronauts' exploration of the tombs gave Xznaal a pretext to claim grave desecration, a crime under Martian law that justified conquering the the United Kingdom as reparations. Xznaal was crowned King of England and Greyhaven became acting Prime Minister.
This was all part of Greyhaven's plan to acquire Martian technology to make Britain great again, in exchange for a method to refertilise Martian soil. However, when Alexander Christian provided him evidence that Xznaal was conducting experiments on British prisoners, Greyhaven saw that Xznaal had broken their agreement. This made him initiate his backup plan.
The reason he had killed the Orbiter crew was so the ship would be available for Greyhaven to use as a last resort. He activated the Orbiter's rockets and set it to crash into Xznaal's clan home. Though Xznaal found Greyhaven and killed him, the Ice Lord was unable to stop the Orbiter from annihilating his entire clan. (PROSE: The Dying Days)