The Bank Job

The British Security Services (MI5) have taken interest in a safe deposit box that is located in a bank on Londonâs Baker Street. It belongs to a black militant gangster, Michael X (Peter de Jersey), and contains compromising photos of Princess Margaret,[6] which he is keeping as insurance to keep the British authorities off his back. Martine (Saffron Burrows), an ex-model who is romantically involved with an MI5 agent, is caught smuggling drugs into the country, and to avoid going to jail she makes a deal with the authorities in which she agrees to retrieve the photos.
Martine approaches her friend Terry (Jason Statham), a struggling car salesman with criminal contacts, and tells him if he can assemble the gang to help her rob the bank he will be richly rewarded, though she does not tell him about the photos in the deposit box. Terry recruits a small team, including one of his own workers, Eddie (Michael Jibson), to serve as the look-out, and Dave (Daniel Mays), a porn actor who once made films for Lew Vogel (David Suchet), a gangster whom Dave happens to run into outside the bank before the robbery.
The gang tunnels their way into the bank vault, where they steal money and other valuables, but Terry is suspicious when he notices that Martine only seems to be interested in one box containing nothing but photographs. After they escape together, Terry throws off a pursuit by MI5. By now the police have been alerted to the robbery by a ham radio operator who has picked up the "chatter" from the gang's walkie-talkies, and Lew learns that among the missing safe deposit boxes is his own box, which is full of evidence about his payoffs to crooked cops. He notifies a furious Michael X in Trinidad, who correctly suspects Gale Benson (Hattie Morahan), Hakim Jamal's lover, of spying for MI5, and subsequently murders her. Lew decides that Daveâs presence outside that particular bank was not a coincidence, and has him tortured for information. Dave gives in, and Lew goes to Terryâs garage to kidnap Eddie. Meanwhile, a government minister learns that he is also featured in some of the stolen photos, and persuades MI5 to give the robbers new passports and safe passage in exchange for the photos in order to avoid a scandal.
One of the crooked cops on Lew's payroll shoots Dave, and threatens to shoot Eddie unless Lew gets his evidence back. Terry agrees to deliver it to him at Paddington station at the same time he is supposed to be picking up his new passports from MI5, but has meanwhile passed on the details to an honest cop, Roy, who alerts MI5 agents. During the exchange, Lew recognises the agents, and he and the corrupt cops make a run for it. Terry pursues Lew and proceeds to beat him up, but Roy breaks up the fight and arrests Lew and his colleagues. In Trinidad, Michael X is also arrested. With his freedom and his new passport, Terry and his family are seen enjoying a carefree life on their small motor yacht off a sunny beach.
According to the epilogue, the corrupt police officers on Lew's payroll were duly investigated, and Michael X was hanged for Gale Benson's murder. It also says that Michael X's personal files are to be kept hidden until 2054 and that Â£4 million worth of property was stolen. Lew was imprisoned for eight years for crimes unrelated to the robbery. At least 100 safe deposit box owners have neither claimed insurance nor identified the items in their boxes.

Question: Why was Gale Benson murdered?
Answer: suspected of spying for the MI5