In his boyhood, Lord Jellicoe was known as the boy who never was afraid. It is told that one day he annoyed and alarmed his nurse very much by racing across a busy street, winding his way in and out between passing vehicles as if he took pleasure in being in danger. In vain she scolded him. Then she said: "I shall tell the first policeman I meet regarding you." Master John did not seem to be the least alarmed by this grave threat. He walked along, smiling to himself, and when he saw a policeman approaching ran up to him and exclaimed: "Oh, what a lot of pretty buttons you've got on your coat!" Master John was not easily scared.

It is not surprising that such a high-spirited boy, with the blood of generations of sailors in his veins, should have been attracted by the sea. He was never happier than when he wandered about Southampton docks watching ships coming and going, and he delighted to hear his father describing his voyages to distant lands. After he learned to read he took pride in the career of his great-grandfather, who had fought and distinguished himself under Admirals Hawke and Rodney. He was quite young when he expressed the desire to enter the navy. His father agreed that he should do so, but made him understand that he would have to study hard to pass the examinations, so that he might become an officer like his great ancestor.

In time the boy was sent to school at Rottingdean, and there he worked very hard to secure the reward which he greatly sought. He delighted his teachers by the way he applied himself. On 15th July, 1872, a few months before he had completed his thirteenth year, he entered the Royal Navy as a cadet. On the training-ship Britannia he studied so well that he took over too marks at the final examination and won all the first prizes. He continued to study as a midshipman, and at nineteen passed as a sub-lieutenant, taking three prizes. Before he was twenty-one he was appointed lieutenant, and then he had three first-class certificates to his credit. The future admiral spared no pains to become efficient and worthy of promotion.

Lieutenant Jellicoe served on H.M.S. Agincourt  when the Egyptian war broke out in 1882. His ship did not take part in the bombardment of Alexandria, but kept watch on other towns and on the Suez Canal. On his return home he continued his studies and won the £80 prize for gunnery lieutenants. Afterwards he was selected as a junior staff officer of the gunnery school at Portsmouth.

That Jellicoe was a heroic sailor, as well as a clever student, was first proved when he served as gunnery lieutenant on H.M.S. Monarch. One stormy day a steamer stranded on a sand-bank near Gibraltar. High seas broke over it, and Jellicoe commanded a boat which attempted to reach it so as to rescue the crew. After a stiff struggle the boat was upset. Fortunately the occupants had been provided with cork jackets and were able to reach dry land safely. The lieutenant was awarded a Board of Trade medal for his gallantry.

He had another narrow escape from drowning in 1893, when he served as lieutenant-commander on H.M.S. Victoria, the flagship of Vice-Admiral Tryon, of the Mediterranean Fleet. On 22nd June important manoeuvres were being carried out. Jellicoe was not on duty at the time. He lay in his cabin, suffering from malaria. In the afternoon the vessels were formed into two parallel lines, led by the Victoria  and Camperdown. Then the Vice-Admiral gave an order to turn inwards, but unfortunately miscalculated the room required by the leading vessels to perform the manoeuvre. The result was that the Camperdown collided with the Victoria  and tore open a huge hole in its starboard side. Vice-Admiral Tryon attempted to run the vessel to the shore, but she settled down by the bows, heeled over, and sank about fifteen minutes after she had been struck. Every man stood bravely at his post until the last minute. About half of the crew, including the admiral, were drowned and about half were rescued.

Commander Jellicoe was summoned by his servant, who explained hurriedly what had occurred. He leaped from his bunk in his pajamas, but before going on deck to try to save his life he went below to hurry up anyone who might be there. When he reached the bridge the Victoria  was sinking fast, and he was thrown into the sea. He sank, but afterwards rose to the surface. As he had been weakened by fever, he would certainly have gone down again but for Midshipman West, who swam to his assistance and kept him afloat until they were both rescued.

The scene was a terrible one. Several men who leaped over the stern of the Victoria  were cut to pieces by the revolving screws. Others who were swimming strongly were engulfed when the boilers of the sunken vessel exploded and threw up great volumes of water. Boats from the other war-ships hastened quickly to rescue the survivors. Fortunately the Camperdown, which was also badly injured, kept afloat in consequence of the cool and collected manner in which Admiral Markham, its chief commander, took precautions to avoid further disaster.

Four years later Jellicoe was promoted to the rank of captain, and served under Admiral Seymour on the China station on board H.M.S. Centurion, the flagship. In 1900 an war broke out in China. It was known as "the Boxer rising". The "Boxers" were members of a secret society who had armed themselves to put down the reform party and drive all Europeans out of the country. Missionaries and traders were tortured horribly and put to death, as were also Chinamen who did not favour the Boxer movement. China was thrown into a state of turmoil. When word was received from Pekin, the capital, that the Legations of the various foreign Powers, in which Europeans had taken shelter, were in danger of being overwhelmed, it was resolved to send an armed expedition from Tientsin, a distance of about 90 miles. This relieving-force was 2500 strong. It was composed of mixed nationalities and commanded by Sir Edward Seymour, who selected Captain Jellicoe as his chief staff officer. Three trains left Tientsin with the fighting-men, but the line was cut near Lo Fa. An attempt was then made to march to Pekin; but strong forces of Boxers not only resisted the advance of the Allies, but got in between them and Tientsin. Sir Edward Seymour, after fighting stiff engagements, and finding the enemy greatly outnumbered his force, decided to retreat. He abandoned the railway line and fought his way back to Tientsin.

At a stiff engagement at Pietsang, Captain Jellicoe, who had conducted himself with great gallantry, was seriously wounded. He was specially commended in dispatches by Sir Edward for his "judgment in action", and "most valuable help". In consequence he was subsequently made a Commander of the Order of the Bath. The Kaiser conferred upon him the Prussian Order of the Red Eagle of the Second Class, with crossed swords.

Pekin was ultimately reached by an army of 20,000 allied troops under Lieutenant-General Sir Alfred Gaselee.

After Captain Jellicoe's return from China he occupied important naval posts on sea and on shore. He was associated with Sir Percy Scott in encouraging good shooting and in generally promoting efficiency. As Director of Naval Ordnance he was a member of the Dreadnought Design Committee. When that historic battleship was launched, King Edward conferred upon him, in recognition of his services, a Knight Commandership of the Victorian Order. Afterwards he was promoted to the rank of Rear-Admiral. He became a Vice-Admiral in 1911, when he received the appointment of Commander of the Second Squadron of the Home Fleet. A year later he was selected as Second Sea Lord of the Admiralty.

Important naval manoeuvres were carried out in 1913. In these Britain was represented by the Blue Fleet under command of Admiral Sir George Callaghan, which was supposed to defend the coast. The enemy was represented by the Red Fleet, under command of Admiral Sir John Jellicoe. The result of the manoeuvres has been kept secret, but it is known that Jellicoe achieved successes by the clever manner in which he conducted operations. He lured away the defending fleet and landed troops on the Yorkshire coast. A raid was also made on Sunderland.

When war with Germany was imminent, Sir John Jellicoe was appointed to the supreme command of the Home Fleets. He selected H.M.S. Iron Duke  as his flagship. From His Majesty, King George, he received the following message:

"At this grave moment in our national history I send to you, and through you to the officers and men of the fleets of which you have assumed command, the assurance of my confidence that under your direction they will revive and renew the old glories of the Royal Navy, and prove once again the sure shield of Britain and of her Empire in the hour of trial."

After serving for two years and four months as commander of the Grand Fleet, Sir John was appointed First Sea Lord of the Admiralty. His successor in the Fleet command is Admiral Sir David Beatty, who, as Jellicoe testified in his dispatch on the battle of Jutland, "had once again showed his fine qualities of gallant leadership, firm determination, and correct strategic insight".

This great battle emphasized the superiority of the British navy, even when matched against odds, as was the case during the earlier part of the action.

Sir John acquitted himself with distinction as First Sea Lord for a period of thirteen months. He was suffering from illness when he resigned in December, 1917.

In recognition of his services, the King conferred upon him a peerage, and he became Viscount Jellicoe of Scapa.

Vice-Admiral Sir Rosslyn Wemyss was appointed First Sea Lord in succession to Lord Jellicoe.