Brain Games, National Geographic Channel’s hit series which seeks to answer some of the most fascinating questions regarding one of our most perplexing organs, made a triumphant return last night. For its fifth season premiere, host Jason Silva took the show on the road to London, where participants helped to demonstrate a variety of functions related to the brain, including how to control one’s startle response and the importance the hippocampus plays in memory.

For the latter experiment, mental_floss was on the set at Hever Castle, the childhood home of Anne Boleyn in Kent, where three individuals—a 10-year-old puzzle enthusiast, a Ph.D. math student, and a longtime London taxi driver—were tasked with running through a 100-year-old Yew Maze, following the exact path mapped out by the show, without making a mistake.

In the end, it was the cabbie, Mark, who emerged victorious. Which was hardly surprising to Dr. Rebecca Knight, who studies memory at the University of Hertfordshire, and was on hand to oversee the maze run.

“If you’re trying to remember what you did last weekend or how you celebrated your last birthday, [those memories] will always have two components to them,” Knight explained. “One is a time component and one is a spatial component. And that memory requires a part of the brain called the hippocampus.”

The hippocampus, which Silva described as the place “where your brain processes memory,” is of particular importance to London taxi drivers. “In order to become a London cabbie, you need to pass a test called The Knowledge, which would require a cabbie to memorize the location of over 25,000 streets [and landmarks] in London,” Knight said. “So they’re excellent navigators.”

Officially known as the Knowledge of London Examination System, the world’s toughest geography test requires years of study and often takes as many as a dozen attempts to pass. (Even then, only about 50 percent of people actually pass it.) It’s a long and difficult process, but one that has piqued the interest of neuroscientists.

In 2000, researchers at the University of London determined that studying for The Knowledge caused the cab drivers’ gray matter to enlarge in order to store a full map of the city. “There seems to be a definite relationship between the navigating they do as a taxi driver and the brain changes,” lead researcher Dr. Eleanor Maguire told the BBC. “The hippocampus has changed its structure to accommodate their huge amount of navigating experience.”

Maguire continued to study the link between navigating London’s labyrinthine streets and brain structure over the next decade. In 2011, she and Dr. Katherine Woollett published a study in Current Biology, which suggested that learning, even in later life, can alter one’s brain structure.

“By following [79] trainee taxi drivers over time as they acquired—or failed to acquire—The Knowledge, a uniquely challenging spatial memory task, we have seen directly and within individuals how the structure of the hippocampus can change with external stimulation,” Maguire said. “This offers encouragement for adults who want to learn new skills later in life. What is not clear is whether those trainees who became fully-fledged taxi drivers had some biological advantage over those who failed. Could it be, for example, that they have a genetic predisposition towards having a more adaptable, ‘plastic’ brain? In other words, the perennial question of 'nature versus nurture' is still open.”

One only hopes that Maguire and her colleagues have time to determine that. In late 2015, the Greater London Authority Conservatives suggested that The Knowledge be done away with altogether, calling the test "archaic" in the age of GPS. In response, a representative for London’s black-cab drivers said that they were “stunned and shocked” by the suggestion.

"I drive a London taxi,” Brian Nayar, a cabbie and Knowledge instructor, told NPR. “But I'm also an ambassador for this great city that we work and live in, and you can't get that from a GPS."

Brain Games airs on National Geographic Channel on Sundays at 9 p.m. ET/8 p.m. CT.