- "You know, my mother's always telling me, never put anything in writing. And now, thanks to you, I never will again."
- —The Duke of Crowborough to Thomas.
The Duke of Crowborough is a family friend of the Crawleys. Little is known about his life, other than that he is a professed student of architecture. Lady Mary Crawley was originally supposed to marry her cousin, Patrick Crawley who was heir to Downton, but she privately held him "in check" for a bigger fish. With his death in 1912, she believed her own prospects have changed for the better. She immediately angled to wed the young and handsome duke. Carson felt it was an honor for the house to have a duke visit, and was certain Mary would make an excellent duchess.
The Duke arrived at Downton Abbey, ostensibly to present his condolences, although he did not really know Patrick except "to see Patrick at the odd thing." Sarah O'Brien made new valet John Bates fall after knocking over his cane, right in front of the Duke and Crawley family. Anna helped him back up while the family went inside.
After dinner the duke requests an interview with Robert, presumably to ask for Mary’s hand in marriage. But when he learns that Robert was not intending to challenge the entail on the estate which now made his unknown cousin Matthew his heir, the Duke withdrew his offer without ever in fact making it. The Duke told then-footman Thomas Barrow that if he married it would be to an heiress, even it means him going to New York to find one.It was revealed that Thomas had brought the Duke to Downton, with a telegram luring him with the prospect of marrying Mary for the Grantham money. After the Duke had previously visited the Crawleys in London, he and Thomas shared a summer dalliance. Thomas had intended to become the Duke's valet after the wedding. When this fails, he attempts to further his own career using blackmail, by threatening the Duke with love letters that the duke had written to him. However, the Duke was one step ahead of Thomas, using Mary as a cover to go exploring the servant's wing, he had rummage through Thomas' room. Thomas, held back by the duke, could only watch as the incriminating letters went up in the flames, after the Duke threw them into his room's fireplace. Robert later told his wife that he was not happy about Mary being pursued by a man who had turned out to be a golddigger, though Cora reminded him he had been one himself when he courted her, and they turned out well.
The following morning, the Duke left Downton. Bates was about to leave with him, as he had been fired and was being dropped at the train station, but Robert stopped the car at the last minute and let Bates stay, telling Carson that it did not feel right.
- In the series he was never referred to by name, only his title has ever been mentioned. In the script for the first season his name was revealed to be Philip.
- Though he never officially stated why he was desperate to marry an heiress, it is most likely he was having financial problems, just like Robert when he married Cora.
- So far, the Duke is Thomas' only known lover. Thomas expressed his love for him, saying he wanted to be with him, but whether his feelings were genuine or if it was just a means to an end is never stated. Thomas never mentions him afterwards.