It is claimed that Albert Walker, 52, murdered Ronald Platt in 1996, after becoming "exasperated" at his failure to lead an independent life, which would have protected the Canadian from discovery.
Exeter Crown Court heard that Mr Walker, who denies the charge, fled to Canada with his daughter Sheena, now 22, in 1990 following the break- up of his marriage and an impending and costly divorce settlement.
Charles Barton, for the prosecution, said Mr Walker had left Canada, where he ran a financial services business, with "various substantial sums, not all of which belonged to him". Charges relating to that were laid against him.
Over here, he first assumed the identity of a David Davis, and his daughter used the name Noel. They lived in a flat in Chelsea, but later moved to Harrogate. There they met and befriended Mr Platt, 51, and his girlfriend, Elaine Boyes, who were offered financial help in 1992 to move to Canada, which they accepted.
Miss Boyes spent two hours pouring out her life story to Mr Walker. "He had clearly gained her confidence," said Mr Barton.
The court was told that Mr Walker, of Woodham Walter, Essex, subsequently assumed Mr Platt's identity, running credit cards and bank accounts in his name. His daughter became Noel Platt and began to pose as his wife. She bore two children, but the court was not told the identity of their father.
Mr Barton said Mr Platt had been "obsessed" with Canada, where he had spent time as a child. But he and Miss Boyes were not successful in carving out a new life. She returned to England the following year, and Mr Platt, who had trouble making ends meet, returned in 1995. By that time Mr Walker and his daughter had moved to a village near Chelmsford, Essex, where he had started a counselling business.
Mr Walker supported Mr Platt on his return until July 1996, when the Englishman disappeared. His body was dredged from the sea-bed by a trawler off Teignmouth later that month.
Mr Platt was only identified through a Rolex Oyster watch on his wrist which bore a reference number that allowed Devon police to trace its owner: the real Ronald Platt, and subsequently his family.
"The irony is that the watch was one of his proudest possessions and never left his wrist," said Mr Barton, who added: "The person who put him on the sea-bed left it with him."
The prosecution claimed Mr Walker threw Mr Platt over the side of his 24ft yacht Lady Jane off the south Devon coast - after tucking a 10lb anchor into his belt to make sure he did not surface.
Mr Barton said that Mr Walker failed to mention the death in a later conversation with Miss Boyes. He had told her that Mr Platt had left for France using capital that he had provided.
The case continues.