Bayldon Copper
Mr Copper was an employee aboard the Titanic who met the Tenth Doctor and Astrid Peth. After the near-destruction of the vessel, the Doctor allowed him to live in 21st century England.
Mr Copper was a travelling salesman, but he reached retirement with little to show for a life's work. He pretended to have a first-class degree in "Earthonomics" to get the job of Ship Historian. In reality, he had been a student at Mrs Golightly's Happy Travelling University and Dry Cleaners. Copper helped the Tenth Doctor defeat the Host. After this adventure, he was stranded on Earth with nothing save the clothes on his back and a million-pound credit card. He had been issued this by the Capricorn Cruise Lines for purchasing trinkets from the local life forms, including samples of their local delicacy, beef.
After being refused an opportunity to travel with the Doctor (because the Doctor did not want a new companion at the time), the Doctor told Copper that the credit card he had was worth the local equivalent of 50,000,056 credits. Ecstatic at his newfound wealth, he planned to make a life on Earth so he wouldn't spend the rest of his life in prison on Sto for fraud. (TV: Voyage of the Damned)
Mr Copper eventually used some of his wealth to establish the Mr Copper Foundation, an organisation dedicated to advancements in science. (PROSE: "Putting Things Straight") Among the Mr Copper Foundation's creations was the Sub-Wave Network. (TV: The Stolen Earth)
Personality
Mr Copper pretended to be knowledgeable about Earth, but often made mistakes describing the planet and its inhabitants' customs. Copper had been a travelling salesman, but felt that he had not been able to accomplish anything in his life and lied to get a place on the Titanic. Nevertheless he was a kind-hearted man, following the Doctor loyally and hoping to travel with him. He also tried to comfort the Doctor about the death of Astrid Peth, telling him to let her go. Mr Copper was ecstatic to find out he was a millionaire and promised to make the Doctor proud. (TV: Voyage of the Damned)
Behind the scenes
First name
The first name of this character is sometimes claimed to be Bayldon. But where does Bayldon come from? It's certainly not in the episode itself, nor any other narrative source. Nor does it appear on the end credits of Voyage. Or the final shooting script. Or the official Doctor Who website. Or in DWM 390 and 391, the two issues of DWM most relevant to Voyage. In fact, the first name was such an irrelevance that Russell T Davies once said he couldn't remember it, but that it would make "a great trivia question". (PCOM: Voyage of the Damned)
The reason Davies had anything to remember is because the character used to have a first name. In one of the first drafts, available to read in at least the original edition of Doctor Who: The Writer's Tale, dialogue proclaims that he is Bayldon Copper. However, it was deliberately excised from the final script. Moreover, The Time Lord Letters, an in-universe publication, makes a point to stress that Copper's first name was unknown.
Casting
The late American actor Dennis Hopper was considered for the role of Mr Copper and was later offered the part of Max Capricorn. The actor was interested in appearing in the show, but Hopper's availability proved insurmountable. Ultimately the role went to Clive Swift, who had previously appeared in the Doctor Who episode Revelation of the Daleks as Jobel.
Nevertheless, the eventual prominence of the character, originally envisaged as a much smaller part, is a direct result of trying to get Hopper to play the role. (REF: Doctor Who: The Writer's Tale)
