Brownlee was the youngest athlete in the Olympic triathlon four years ago, when he finished 12th, but has since won two world and European titles and established himself as the world's number one triathlete.
He missed much of the early season with an achilles injury, spending hours training on a water treadmill in his back garden in a bid to get fit.
And that mind-numbing hard work and dedication paid off as underlined his race favourite's status in style.
Great Britain has never won a triathlon medal since the sport made its Olympic debut in Sydney but not only took gold but also bronze, Brownlee's younger brother Jonathan claiming third behind Spanish silver medallist Javier Gomez.
They are the first British brothers to win medals in the same event since Greg and Jonny Searle in rowing coxed pairs in 1992 and the gold moves Great Britain level with the number of podium top places they achieved in Beijing - with six days to come.
Brownlee and his sibling finished the 1.5km swim in the top six and soon started working together in a 22-strong group in the 40km bike leg.
British team-mate Stuart Hayes, one of the strongest bike riders in the race, worked hard on the front fracture the group, while Russia's Ivan Vasiliev also seemed determined to break up the race.
But others, notably defending champion Jan Frodeno and Gomez, seemed content to let the pack stay together and allow the race to be decided on the run, four 2.5km loops of Hyde Park around the Serpentine.
Gomez, a winner on this course two years ago, and the Brownlees were quick to sprint clear, opening up an early 17 second advantage after the first lap with a furious injection of pace.
Huge crowds, ten deep in places, some of whom arrived at 5.30am to secure their position, cheered them around and by the halfway point they'd increased their advantage to 27 seconds.
But Jonathan Brownlee began to struggle with the relentless pace, as his brother started to kick clear, and still he needed to take a 15-second stop and go penalty for an earlier error during the swim/bike transition.
At the start of the final lap Alistair Brownlee was five seconds clear of Gomez while his younger brother was still in bronze after his penalty, with France's Vincent Vidal and David Hauss 13 seconds back in fourth and fifth.
And he kicked clear with victory assured to secure a famous victory, his winning time one hour 46 minutes and 25 seconds as he crossed the line wrapped in a Union flag.