The Hard Rock theme was dreamt up nearly 25 years ago by Peter Morton, who had the idea of packing diners with showbusiness memorabilia, particularly from the music industry. Planet Hollywood also serves burgers and fries in a showbiz setting, but focuses on movies.
Lawyers on both sides expect a verdict in the Los Angeles branch of the US District Court within two weeks. And Rank Organisation, which owns the rights to the Hard Rock Cafe name in Europe and the eastern US, could have to pay a large chunk of the $1.2bn if its side loses.
The case has been brought by Mr Morton, the owner of the rights in the western US and Asia, and his co-investors. He contends that Robert Earl, the Planet Hollywood founder, stole his idea and also that Planet Hollywood restaurants have been deliberately located so as to tempt customers away from nearby Hard Rock outlets.
Mr Morton says Hard Rock's trademarks have been infringed, menus copied, secrets stolen - and that his company has been the victim of unfair competition.
Mr Morton and friends claim $250m in actual damages and $500m in punitive damages. Under US law, an actual damages award would be trebled. Planet Hollywood is defending the claims.
The case dates back to 1985, when Hard Rock was divided. The part covering Europe and the east coast of America was bought by Pleasurama, itself eventually bought by Rank. It was operated by Mr Earl until 1992. He then set up Planet Hollywood, with Rank's backing. Last year, Rank tried to settle the dispute with an out-of-court offer of $3m, but this was dismissed by a member of the Morton camp as "derisory". In recent annual reports, Rank has said it believes the case to be baseless, and that it will not result in a "material adverse affect on the financial condition of the group".
Mr Morton's lawyer, Harry Swerdlow, said yesterday: "My client's concept was stolen and the Hard Rock Cafe deserves compensation. "I would expect a conclusion to this case possibly within a week, or maybe two. I would hesitate to predict the outcome - you never can tell."