When Sir Robert Peel created the Metropolitan Police Force in 1829 he knew that he was doing so without the support of a large percentage of the population. The anxieties of people centred around two facts. First, that the police would 'spy' on them as they went about their everyday activity and second, the militia had been used to break up civil unrest and riot and they often resorted to using their swords resulting in death and injury.
To allay some of this anxiety Peel and his two Commissioners, Sir Charles Rowan and Sir Richard Mayne, decided that the 'new police' would wear a uniform. The idea was that they would then be highly visible so that people would not associate them with the covert activity of spying. In choosing a uniform Peel wanted something that did not associate the police with the militia who wore a uniform of red and gold. So a blue coloured uniform was chosen, one with a tail coat and a black top hat. This made the police look like a locust, hence the nickname 'The Blue Locust.'