How does the Englishman shape the themes and the plot in The Alchemist?

The tale of The Alchemist by Paulo Coelho is a story of a hero's journey, as Santiago ventures to Egypt in search for treasure that he was promised in his prescient visions. Along the way, he encounters an Englishman at an opportune time. Santiago has been robbed on his journey, losing all the money he had to continue in his quest, and considered giving up before working for a crystal merchant, in hopes of just earning enough money to continue his journey. It is here that he encounters the Englishman.
The Englishman acts as a motivator and helps return Santiago to his hero's journey in his own way. While he was languishing working for the crystal merchant, it seemed as if his Personal Legend was slipping further away from him. The Englishman comes in and accelerates the plot, acting almost as a sort of "Deus ex Machina," appearing from thin air to fix the problem. He takes Santiago along with him to find the Alchemist—for the Englishman thinks the Alchemist can bring him riches with his alchemical ability, while Santiago believes the Alchemist can help him find the treasure he is seeking at the pyramids.
Throughout the story, many forces converge to empower and encourage Santiago on his quest—the first being his visions, supposedly from a divine power, encouraging him to set out in search of the riches promised. The next is the ancient king Melchizedek, a biblical precursor to Christ who guided Abraham before the formation of Israel. The final guide is the Alchemist, who helps him arrive at the pyramids and teaches him along the way, but prior to that, the Englishman acts as a guiding force.
The Englishman gives Santiago motivation by taking him as an assistant to find the Alchemist, which breaks him free from his bondage to the crystal merchant but also gives him means. The Englishman takes care of their journey so that it is safe and comfortable, and he smooths the road before him so that Santiago can eventually meet the Alchemist. Thematically, the Englishman acts as one of the many spirit guides that Santiago encounters, even though he is the most physical of the forces at play in the story. He acts as the archetypal "coincidental aid," where it just so happens that the exact person you need shows up in your moment of greatest necessity. This helps to move the plot along but also guides the theme that Santiago is in fact on a divine quest to seek his Personal Legend, because, in spite of the hurdles he must overcome on the journey, provision is always at hand in some form.