British police investigating the terror attack on parliament made a new arrest today as authorities try to piece together the assailant's motive. <br/><br/>London's Metropolitan Police said in a statement that a 30-year-old man was arrested in the central city of Birmingham on suspicion of preparation of terrorist acts. '<br/><br/>A dozen people have been arrested since 52-year-old Briton Khalid Masood launched an assault on parliament on Wednesday, killing four people and leaving 50 injured before he was shot by police.<br/>'<br/>Nine people have been released without charge, while a 58-year-old man remains in custody and a 32-year-old woman has been released on bail. <br/>'''