The British Empire was very much dependent on maritime trade because of the fact that Britain is an island and the fact that so much of its empire was so far away. Therefore, it had a strong interest in protecting its trade routes. It did this in two major ways.
First, it maintained a very strong navy. Britain had the strongest navy in the world from at least the 1600s until WWII. Britain was constantly working to make sure it kept this advantage, as with the creation of the Dreadnoughtclass of battleships that were created to make sure the Royal Navy remained superior to Germany's navy.
Second, the British took control of strategic areas on the land. The most important example of this was northeast Africa. Soon after the Suez Canal opened, Britain realized its strategic importance. Therefore, Britain soon came to dominate the area of Egypt and Sudan that control access to the Suez Canal.
In this way, Britain protected trade routes both by land and by sea.