Single mother Christina Weckwerth and chiropractor Jessica Mang didn't know each other even existed, yet they shared two things in common, British prosecutors say. Both were lovers of the same Mizuho International investment banker, Thomas Ammann, and both reaped large rewards as a result of his illegal insider tips on the same stock, in Weckwerth's case turning a US$1.3 million stake into nearly US$3.2 million, said Amanda Pinto, a lawyer for the UK Financial Services Authority. Mang, a British chiropractor, realised £65,000 (HK$810,000) on a £39,000 (HK$486,000) stake, said Pinto in opening arguments at a London criminal court on Tuesday. Both women were trading on illegal information and tips about Canon's acquisition of Oce NV, prosecutors said. "Each of the girlfriends considered Thomas Ammann to be their boyfriend, and neither knew of the other," Pinto told the jury. Both paid half the profits they made to Ammann, Pinto said. Weckwerth was charged with one count of insider trading between April and November 2009, and Mang with one count of insider trading in November of that year. They have pleaded not guilty. Insider trading in the UK can be punished by as much as seven years in prison. The tips came about after Canon, the Tokyo-based maker of cameras and photocopiers, agreed to buy Oce NV in a €730 million (HK$7.3 billion) deal in November 2009. Ammann, who worked for the Mizuho mergers and acquisitions team that advised Canon on the deal, pleaded guilty earlier this year to insider trading and encouraging both women to commit insider trading, Pinto said. The banker had been experiencing financial difficulties and was living beyond his means, Pinto said. Weckwerth, a single mother living off a "very generous divorce settlement" of €1.7 million met him in 2008 on a dating website, the prosecutor said. "He had the inside information, they had the money," she said. Weckwerth had "invested conservatively" before meeting Ammann, Pinto said. Her trading in Oce shares "was quite exceptional" in comparison, she said. Mang, who now owns a chiropractic clinic in Surrey, England, met Ammann at a nightclub in July 2009, Pinto said. When he first asked her to invest, she didn't have the money or a trading account. He told her she would get returns as high as 80 per cent, so she borrowed money from her mother and on credit cards. Mang bought Oce shares and then sold them five days later for almost twice what she invested, Pinto said. Mang wrote in her personal diary that Ammann advised her to invest, she said. Mang had been living in central London with a friend who worked in hedge-fund sales for Goldman Sachs, Pinto said. When told about Mang's plans to invest in Oce, the friend "expressed disapproval, calling it insider dealing".