Complex sentence: The first modern police force is commonly said to be the London Metropolitan Police, established in 1829 by Sir Robert Peel, which promoted the preventive role of police as a deterrent to urban crime and disorder.
Split into simpler sentences: The first modern police force is commonly said to be the Metropolitan Police in London, established in 1829 by Sir Robert Peel. Based on the Peelian principles, it promoted the preventive role of police as a deterrent to urban crime and disorder.