Tower of London has a new ravenmaster. His mission is unflappable.

If an ancient prophecy is right, Michael “Barney” Chandler has just got the most important job in England.

The former Royal Marine is the new ravenmaster at the Tower of London, responsible for looking after the feathered protectors of the 1,000-year-old fortress.

According to legend, if the ravens leave the 11th-century tower beside the River Thames, its White Tower will crumble and the Kingdom of England will fall. In the 17th century, King Charles II was told of the prophecy and decreed that there must always be six ravens at the tower.

“We take that responsibility very seriously,” said Mr. Chandler. “And now that I’m ravenmaster, there’s that extra responsibility on my shoulders.”

As for the prophecy, he said “we don’t know if it’s true or not, because we’ve never let the number drop below six – and it’s not going to happen while I’m here.”

Mr. Chandler, who officially takes up the post March 1, is one of the tower’s famous Yeoman Warders, part of a corps founded in the 15th century. Also known as Beefeaters, the warders are all military veterans who dress in distinctive black and scarlet Tudor-style uniforms and perform a hybrid role: providing security, leading tours of the tower, and performing ceremonial duties.

He heads a team of four other Beefeaters looking after the tower’s seven ravens – the six decreed by Charles II and a spare. They are Jubilee, Harris, Poppy, Georgie, Edgar, Branwen, and latest addition Rex, who was named in honor of the coronation of King Charles III last year.

The jet-black birds are a familiar feature at the landmark, which has served as arsenal, palace, prison, zoo, and more recently tourist attraction.

Kirsty Wigglesworth/AP

The Ravenmaster's badge on Barney Chandler's red-and-black uniform. "They're always trying to catch us out," Mr. Chandler says of the clever birds.

Built by King William I after his conquest of England in 1066, it served as a royal residence for several hundred years, but is more famous as a prison.

The Tower is where “the princes in the tower,” sons of King Edward IV, were confined in 1483 and allegedly murdered by their uncle, King Richard III, and where Anne Boleyn was executed in 1536 after Henry VIII grew tired of his second wife. Other famous inmates have included Princess Elizabeth, the future Queen Elizabeth I; Guy Fawkes, who tried to blow up Parliament; and Adolf Hitler’s deputy, Rudolf Hess.

Nowadays, almost 3 million tourists come each year to soak up a millennium of history and see the glittering Crown Jewels, which are stored in the tower.

The official title of ravenmaster is only 50 years old, though the role is far older, and Mr. Chandler is the sixth holder of the post. He is in charge of the health and welfare of the birds, who usually roam freely around the tower grounds by day and sleep in cages at night.

Duties include maintaining the birds’ enclosures, arranging veterinary checkups, and keeping them fed on their preferred diet of raw meat supplemented by the occasional treat of a hard-boiled egg or a hard-tack biscuit soaked in blood.

“They’re carrion birds,” said Mr. Chandler. “They’ll eat almost anything.”

The birds’ feathers are trimmed to prevent them flying away, although they occasionally escape. According to Historic Royal Palaces, the charity that oversees the tower, a raven called Grog flew off in 1981 and was last seen outside an East End pub named the Rose and Punchbowl.

Mr. Chandler is endlessly fascinated by the highly intelligent birds, which he says are as smart as a 7-year-old child. Pressed on his favorite, he names the mischievous Poppy, who hops across the grass beneath the White Tower and eagerly accepts his offering of a dead mouse as a snack.

He says the bright-eyed corvids are “probably one of the most intelligent animals there are. Sometimes, here, too clever for their own good. But for me that’s the attraction.”

Mr. Chandler, who served in Afghanistan and around the world during 24 years in the Royal Marines, has been on bird handling courses and had other formal training for his role. But he says “all the courses in the world doesn’t replace actually being here and being amongst the birds and knowing their habits.”

“You never know what they’re going to do,” Mr. Chandler said. “They’re all totally different, personality-wise. Some will play ball, but others won’t. It’s just the unpredictability, which is also the interesting part of the job.”

“They’re always trying to catch us out,” he said fondly. “They know what we’re up to.”

This story was reported by The Associated Press.