Sea power, merchants, and luck.

While the British were not always the best at sea power, from the time of the Armada onwards their power of naval projection grew stronger and stronger. This was aided by the fact that British merchants got more and more involved in intercontinental trade, with Africa, America, the Spice Islands, India, etc.

The more money came into Britain, the more money they could put into their navy, which then could protect the trade lanes, allowing more trade, which meant more money. This, combined with Britain founding colonies in multiple places like what became the United States, then being those colonies exclusive trade partners (Which was actually one of the factors in the start of the War of Independence), allowed for Britain to build an almost complete hegemony over the seas with time.

At different times their growing power was contested, first by that other great trading nation of Europe, the Netherlands. This led to a few Anglo-Dutch wars, which eventually led to Britain being the main naval power in Europe.

The next people to contest this power were the French, who also wanted naval and mercantile power in America and other places. This was one of the reasons the French were willing to aid the colonists in America during the War of Independence (Which coincidentally helped to bankrupt them). It was also one of the many reasons for the previous Seven Years War (Known to the Americans as the French and Indian war, even though it was a much more global conflict than that), one of the first ever (sort of) global conflicts.

After multiple wars with the French, both before and after the French Revolution, British naval power was almost completely uncontested. They had broken the French navy at Trafalgar, bringing to an almost complete end the naval part of the Napoleonic wars. British naval power was from then on unchallenged by the French, which allowed them to begin blockading French ports (A tactic they could then use to great effect in the First World War against Germany).

The amount of money that their merchants brought in allowed the British to support such a powerful navy, and to support trade lanes with it. Taking control of large territories such as South Africa, Canada, Australia and India, and colonising them all to varying degrees, allowed them to have sources of prime materials for the factories that had sprung up in Britain.

The Industrial revolution was born in Britain in the 1700s, and allowed huge economic growth, which brought even more money in, allowing them to become still more powerful, economically, politically and militarily, in the process.

Anyway, that is a simple history of it all.

I would say that the English had the benefit of a channel buffering them from the endless land wars on the continent. As an island they had to depend on shipping for commerce and defense. The country worked hard to establish a Navy in the 16th century under Elizabeth. This Navy was strengthened by continual administrative changes in policy. For example, the Crown made it so that only English ships could bring goods from English colonies to England. They also required English colonist or citizens be predominate members of the crew. As such they had fleets of ships, many armed, that could be used as needed to protect both the Empire and the Homeland.

Additionally some powers were not interested in running countries and nation building but in making money. The Dutch, Northern Italian states, U.S.A. and the Portuguese (in Asia) did not care who was in charge of the country as long as they had friendly trading partners. They essentially allowed Britain to take over the policeman role so long as they made money. Ultimately this was England's downfall as its Empire was so over stretched it made it so expensive to maintain it had to be let go. The fall of the American Colonies was more about revolt over the cost of fighting to keep them than in military supremacy of the rebels.

One major difference between England and the rest of Europe was the development away from absolutist regimes:

• the Magna Carta issued in 1215 limited the kings power over the nobles

• serfdom disappeared in Britain during the 15th-16th century

• the English civil war period from 1642–1651 resulted in the parliament becoming a major political power

• the Glorious Revolution in 1688 established a constitutional monarchy in England, effectively giving the parliament control over most of the legislaltive

These events were crucial for the development of the English economy that enabled the industrial revolution. Under the arbitrary rule of a feudal absolutistic regime it is difficult for anyone to make investments in the future, ranging from the farmer who doesn't deem it worth to invest in soil improvement because the lord could just take more of his harvest to the enterpreneur who wants to set up a business but is hindered by monopolies given to someone else.

Basically the political system created incentives for people to invest in their business by giving them the means to influence lawmaking in order to protect it and making sure taxes are fair, creating demand for new technology and increasing the tax revenue. This was a significant advantage over the other comparatively stagnant European powers.

The book "Why nations fail" by Daron Acemoglu and James Robinson goes to great length about this topic