For centuries the coinage of the country was struck within the precincts of the Tower of London until 1806 when the troops retained there encroached on the little space available for coining. New buildings were then erected on Tower Hill and the Mint was relocated in 1811 to its present location. A guard for the Mint continued to be furnished by the regiment in residence at the Tower and was gradually reduced in strength until it numbered only nine men in 1903. These men fulfilled the duty other than in the summer months, when the absence of the Guards on training rendered it necessary for a line regiment to take their place.

Beginning in 1901, one Sergeant and five Police Constables of the Metropolitan Police 'H' Division were specially engaged at the Royal Mint to share protection duties with the military guard at a cost of £923 per year. It was not unusual for the Metropolitan Police to provide Officers for special protection as it was done contemporaneously at many locations across the country including the British Museum, the House of Lords, the House of Commons, Sandringham and at naval establishments, to name but a few. In exchange, the Metropolitan Police Force was paid for these special police duties. The same services were also available to and paid for by some public companies and private individuals.

In May of 1903, the Secretary of State for War made the decision to abolish the military guard at the Royal Mint altogether, with a view of relieving the excessive amount of sentry duty performed in London. Although no official reason for the action was given it was widely acknowledged that the threat level to the Mint had waned to the point that it left the Mint Guard fulfilling only an ornamental function. In keeping with the decree, at half-past nine on Wednesday morning, 1st July 1903, Sergeant Manley, a Corporal, and nine men of the 4th Rifle Brigade lined up in front of the Mint, presented arms, and then marched away to the Tower, thereby dismounting the Mint Guard for the last time. The buildings and grounds of the Mint were then entrusted for the purposes of protection entirely to the Metropolitan Police. The Metropolitan Police presence was doubled as a result, increased by one Sergeant and five Police Constables, from 1st July. The additional men increased the annual expenditure by a further £923, making the annual amount due to the Metropolitan Police Force £1,846, with payment the responsibility of the Office of Works. By 1908, the cost of these special services was £1,718 10s 10d and it increased to £2,555 by 1914.

Over the years the contingent of Metropolitan Police Officers at the Mint consisted of between twelve to fifteen men, comprised of one to two Sergeants with the remainder being Police Constables. Although dedicated to protection duties at the Royal Mint they continued to report to their superiors within the Metropolitan Police rather than the Mint authorities.

Security arrangements were strict at the Mint as one might imagine. At the outermost reaches of the grounds there was an iron gate as well as a moat in front of the building that was seven to ten feet deep. The moat was later filled in and made a flower garden, much to the disdain of the Metropolitan Police guard. Each working Department within the Mint was kept locked during the day. No one could visit a room other than the one they were assigned to without the sanction of their supervisor. When there was movement between spaces the gold pieces were counted as well as weighed for their transit from room to room. The head of each department tracked the weight of metal that was given out to each worker in the morning and, after allowing for waste, determined the exact amount of gold and silver that should be in the hands of each at the end of their day. Even the dust on the floor was taken into account with it being collected and placed into water to separate the gold and silver from the debris. Security measures were not so extreme as to include regular searches of the workers when they went home at night but no employee engaged at the Mint was allowed to leave the building until the day's work was done, taking their dinner on the premises as needed. If a valuable piece of metal went missing from any department the employees in that department had to locate it before they went home. If it was necessary to search an employee that search was not conducted by the Metropolitan Police Officers but by a designated member of staff who was paid extra for the task, an additional 6s a week in 1912.

The face of every official and every one of these workers at the Mint was studied and known to the Metropolitan Police Officers on duty. These Metropolitan Police Officers conducted both day and night watches armed with revolvers, and later automatic pistols, with the Metropolitan Police starting to issue Webley and Scott .32 calibre automatic pistols for Officers on special duty in 1911 (see Issue XIV of The Journal). That the Police Officers at the Mint were armed was a factor in the selection of only very experienced Officers for the duty. Protection arrangements during the day included a soldier, until they were withdrawn in 1903, and a Metropolitan Policeman who mounted a double guard at the outer gate. Each night, from 6:00pm until 8:00am the Police Officers constantly patrolled certain parts of the grounds and buildings including the scale rooms, machine rooms and minting rooms, permitting no one, irrespective of standing or authority, beyond the outer iron gates to enter during those hours. There was even an arrangement at the entrance to the vaults to automatically record the time the Police Constable passed during their rounds. The time of their passing over a grating was checked up against each as they pushed an electric bell.

A death is recorded in October of 1910 of one of the Police Constables assigned to the contingent at the Mint. Shortly after parading for duty at the Mint, PC George Henry Osborne, aged 38, left the Police Lodge at noon on the 14th of October to relieve another man when he suddenly fell to the ground unconscious. He was removed to the Leman Street Police Station where he was examined by the Divisional surgeon and pronounced dead. His death was found to be due to heart failure following pneumonia.

By 1919, the ranks of the Metropolitan Police at the Mint had expanded to include a Police Dog. A cross between an Airedale and an Irish Terrier, the dog was taken to the Mint as a puppy and then carefully trained in his duties. The dog had the advantage of being able to patrol places a Police Constable could not conveniently access. After a certain hour along his beats at the Mint the dog would not allow anyone within a certain distance unless they were wearing Police uniform.

Among the Sergeants assigned for duty at the Mint were Sergeant Morgan Richards. Sergeant Richards was selected for special duty at the Royal Mint in January of 1921, having charge of the Police at the establishment until the time of his retirement in August of 1924, on full pension, after completing 26 years' service. His career with the Metropolitan Police took him far and wide. A native of Merthyr, he joined the Metropolitan Police in July of 1898 and was posted to the 'T' Division at Hammersmith where he was stationed for eighteen months. He was then transferred to the Devonport Dockyard and, after three years' service there was removed at his own request to the 'S' Division at Albany Street, Regent's Park. On promotion to the rank of Sergeant in 1907 he was sent to the 'L' division at Kennington Road and, five years' later was appointed to the Reserve and transferred to Rodney Road Station, Walworth when that body was abolished.

By 1927, the policing arrangements with the Metropolitan Police for the Royal Mint came at a significant annual cost of £7,101. In the name of economy, it was decided to withdraw the Metropolitan Police protection from the Royal Mint on 1st April 1928, replacing it with members of the War Department Constabulary. The Constabulary was established in 1925 as one of the economies to come out of the War Office. An annual savings across the country of between £40,000 and £50,000 had been estimated by substituting these specially enrolled Constables for the ordinary Policemen at the various ordnance factories, depots and stores in England and Scotland. The ex-Servicemen, from which the War Department Constabulary was formed, had a rate of pay substantially lower than that of a Metropolitan Police Constable who were paid £3 10s to £4 10s weekly. Additional increments of 2s 6d weekly could also be granted for good conduct and efficiency after seventeen and twenty-two years' service with the Metropolitan Police. By comparison, rates of pay for the War Department Constabulary ranged up to about 50s a week with the Civil Service bonus added, although each also earned a pension.

The last group of Metropolitan Police Officers to serve at the Royal Mint, two Police Sergeants and thirteen Police Constables, were all long time members of the Force, each with over twenty years of service with the Metropolitan Police before being selected for duty at the Mint. Although whilst seconded they scrutinised the Mint for vulnerabilities as part of their duties, the Mint was quiet at night, with the Officers remarking there were times when they would have welcomed a little excitement, lamenting there were many more happenings for the average Policeman in the streets than for them within the iron gates of the Mint.

The new War Department Constabulary guard for the Mint consisted of fourteen ex-Servicemen in the charge of three former NCO's. The whole of the men were specially chosen by the War Office and Ministry of Pensions and reported directly to the Mint authorities. On the afternoon of the last day of duty for the Metropolitan Police, 31st March, 1928, one of the two Metropolitan Police Sergeants conducted the new men of the War Department Constabulary around the Mint and explained the duties. The Metropolitan Police Officers performed their last duty at the Royal Mint that night with the change over taking place at midnight on 1st April.