The British Government approached Hiram Maxim with a request for a 37mm Maxim gun, similiar in action to the 37mm Hotchkiss. Maxim scaled up his machine gun to fire one pounder shells. The construction was similiar in all respects, but on a huge scale. The speed had to be reduced to 300 rounds per minute, and was a wild success. Africans who heard the gun in action called it the pom pom, from it's distinctive sound while firing full auto.
The only problem for the British was that the shells cost too much. At 6 shillings per shell the Brits thought a bit much at 300 rounds per minute. British Artillery experts thought little of the gun. Too big to be used against personnel and too little to battle artillery, they turned it down.
The guys who didn't turn it down were the Boers, soon to be in conflict with the British Army. They got them from the French, who bought quite a number of the guns for themselves. The guns were using smokeless powder by this time, reducing their chances of a concealed gun being spotted. The Boers would have one hidden close to a British artillery battery, and fire one ranging shot. If on target, the Boers would let it rip, putting an entire battery out of commission. The British gunners couldn't return the fire effectively with nothing but the sound to fire on.
Needless to say, the British dropped their objection to the price of the shells, and quickly loaded up on 37mm Maxims and millions of rounds of ammunition quickly, The gun was also tried out as an anti-aircraft weapon in the first World War, but the shell was inadequate for the task.