With the large amount of labour employed loading and discharging cargoes in the late 1700's, there were great opportunities of pillage on the River Thames. The River was infested with pirates and thieves with property to the value of nearly half a million sterling stolen in every year. The Customs' revenues of King George III were annually defrauded of £50,000. Many of the Mates and Revenue Officers, instead of being checks on the plunder, proved to promote it. In response to this costly criminal activity it was customary for ship owners to employ watchmen for 4s and 5s per day to guard the cargoes alternately day and night but, even with these men employed, the pillage and plunder went on as before. The system of Police Surveyors, who proceeded every evening from London Bridge to Deptford on both sides from ten at night until five in the morning was also not effective. To combat the problem, on the joint action of the Government and the West India merchants, the Thames River Police were formed in 1798 as the "Marine Police Department" and aptly stationed at what was then the most central part of the Port of London, at 259, Wapping New Stairs. They were placed under the command of Mr James Evans, Principal Surveyor, who for a further fifty years and seven weeks from that date nominally carried on the responsibility of control of the Thames Police. On his retirement, then Superintendent Evans was succeeded by his son, Mr James Christopher Evans, who had joined the Thames Police as a 'Surveyor' in April of 1833. He in turn retired in 1869, after thirty-six and one-half years' service.

The new Marine Police Constables were required to have the best recommendations and were appointed only after a full investigation as to character, ability and fitness to execute the trust reposed in them. They were each sworn to execute a certain duty and to follow specific and clear instructions which were given to them. Unlike the watchmen who preceded them, they were armed with the authority of the law and duly qualified to seize and apprehend all delinquents. They were regularly surveyed by superior officers, both day and night, who inspected into their conduct and reported daily to the Magistrates how far they had conducted themselves properly and in conformity to their instructions. As they derived their authority from the Magistrates, and were accountable to them only for their conduct, and as they knew they would be narrowly watched and minutely examined how well they had performed the duty assigned them, they were set apart from all watchmen. They had to be correct, vigilant and faithful in the discharge of the trust they were sworn to fulfil or they would not only lose their wages but be rendered infamous and punished in case of any criminal connivance.

Many of the old watchmen, on the recommendation of the merchants, were taken on as Marine Police Officers. These men uniformly declared it was impossible to prevent plunder or guard property under the old system for want of that authority they then possessed under the Marine Police and from the precautions taken by the Marine Police including causing a printed paper, entitled, "A Caution", to be nailed to the mast of each vessel warning all persons of their danger in case of detection. A complete change took place on the River under this new system by as early as August of 1798.

Although it was not part of the original plan for the Marine Police establishment to undertake to find labourers to unload the cargoes of West India ships, it was afterwards determined to attach to the institution a department for registering a class of men in order to exclude suspicious characters and to work out the ships they work upon so that they were more immediately under the control of the police establishment. Accordingly, about 70 individuals, capable of acting as foremen, and about 800 men accustomed to unloading West India cargoes, were put on the registers of the office and gangs were aligned to as many of the ships as were applied for.

The master or foreman of each of these gangs was solemnly sworn to perform the peculiar duty assigned him - to permit none of the casks or packages to be wilfully broken, to prevent pillage and plunder and to promote dispatch to the utmost of their power. Six of the old ship masters, who were appointed river or boat surveyors under the Marine Police, had each a division of ships assigned them, which they visited regularly while under discharge, twice in the day, and once during the night. They inspected the work going forward in the hold and upon the deck, and gave such orders and directions for the purpose of promoting economy and dispatch, and of preventing plunder, as their professional and neutral knowledge suggested. They reported their proceedings each day to the Marine Police office. The effect of the system was unmistakable and the saving to the planters, merchants, ship owners, and the Revenue was substantial.

In its forty-first year, the Thames River Police became a special division of the Metropolitan Police, against opposition by the Home Office, on 31st August 1839. Mr Evans continued as Superintendent when the management of the Force was transferred to the Commissioners of the Metropolitan Police. The Force then consisted of a Principal Surveyor, Mr Evans, an Inspecting Surveyor, twenty-one other Surveyors, seventy River Constables and five land Officers. Seven boats, with a Surveyor and three River Constables in each, were constantly on duty day and night. With the change, Mr Evans as the Principal Surveyor was sworn in as Superintendent, the other Surveyors as Inspectors and the River Constables as Police Constables, or Privates of the Metropolitan Police Force.

By 1888, the Division numbered 200 men - a Chief Inspector, seven Inspectors, forty Sub-Inspectors, five Detectives and 147 Constables. In its ordinary routine of daily service, the twenty-four hours of the day were divided into four watches, each of six hours, with boats to come in and go out every two hours, being six hours on and twelve hours off duty. About twenty boats were employed in the rota. Two steam launches were also employed with one constantly inspecting and guarding the bridges and the second used by the Superintendent for visiting the stations at intervals and generally looking after the service. There were duty boats, pulling two oars, and supervision boats, pulling two oars. A pair of skulls were used by the Inspectors to monitor the duty boats were doing their work.

The kind of duties performed by the men of the Thames Division were almost classified by the particular station of the Thames Police where they served. The Waterloo Station saw the largest number of suicides. For their rescue, a special dinghy was always kept ready. It was fitted with a roller on the stern to enable the would-be suicides to more easily be pulled into the boat than by the taxing alternative of lifting them over the side. For 1887, the Thames Police reported twenty-five actual suicides and fifteen more that were prevented by the Police. The latter were generally charged and remanded for the chaplain of the jail to speak with them.

The Station at Waterloo was similar to the landing stages and had a very cosy set of rooms. These included the private rooms, occupied by an Inspector and his wife; a charge room and office, furnished with desks and a telegraph; the reserve room, where the Constables also kept their oil skins; and some other rooms including one for the recovery of persons apparently drowned called the receiving room that was fitted with a bed and a bath with hot and cold water. There were boats lying at the Station and the steam launch 'Alert' was moored off the lower end.

The Headquarters is at Wapping Station, a substantial brick building built in 1869. It contained the cells, the charge room, and the office, which looked out on the River with picturesque views. The primary duties at this station were the protection of the barges and vessels moored in the stream, and also receiving the bodies of persons found drowned. There was a collection of photographs of these unfortunate persons, who were in many cases unknown. At the Wapping Station barges were rummaged as well as any small boats that had been found to be moving about in a suspicious manner. The chief offenders were dredgers, a class of men whose personal appearance and manners, and the dirty boats they possessed, evidently distinguished them from the watermen and pilots. They ostensibly dredged for coal, pieces of rope and other loose articles; but they were often to be seen with their craft loaded to the gunwales with the best coal. However, there was plenty of muddy water at hand, and the coal always had the appearance of having been at the bottom of the river; so that nothing could be done unless they were caught on board the coal barges.

The station at Greenwich was an old six gun brig named the 'Royalist'. It was moored and built up on the river bank with the bilge supported by solid masonry forming a bed that kept the vessel in place. The Royalist had good accommodation on board and was in the charge of an Inspector. The men had the lower deck for their dining and general room and each had a snug cabin with everything kept very neat by its inhabitants. These Thames River Police Officers also found employment protecting the large market gardens in the neighbourhood as well as looking after the dredgers and an occasional stowaway. The Royalist additionally displayed a collection of handcuffs, truncheons and other police implements - an early display preserving and showcasing elements of police history.

A station was also located at Erith, some seventeen miles from Wapping by the River. The meadows and marshes along the lower reaches of the Thames there were previously a hunting ground for sheep stealers. When this practice became too bad, a boat was sent down from the Thames Police Stations with instructions to cruise about there for a week. This practice partially checked it but after that time, the Spray, a small cutter of about ten tons, was then stationed at Erith with sheep stealing almost entirely stopped by 1888.