“My goodness, that was strong talk for an Englishman,” says the Earl of Grantham to his valet, Bates, after a brief discussion of feelings in Season Four of “Downton Abbey.” Though divided by social position, these two Englishmen are among each other’s best friends and allies.

Fast forward nearly a century to two more, very real Englishmen who formed an unlikely and unique bond: James Bowen, a London street musician; and a ginger tomcat named Bob. Bowen tells their story in “A Street Cat Named Bob” (St. Martin’s Press, 2012), subtitled, “And How He Saved My Life.”

Bowen was a recovering heroin addict who, as he describes it, had failed to take any of the many opportunities he’d been given. Then one evening he came home to find a ginger tom curled up in front of the door to one of the ground-floor flats in his building. “There was a quiet, unflappable confidence about him,” Bowen recalled. Having a soft spot for felines, he said, “I couldn’t resist kneeling down and introducing myself.”

He stroked the thin cat’s neck; there was no collar and his coat was in poor condition. Bowen wanted to take the apparently homeless creature home then and there — but his friend said the cat must belong to whoever lived in the flat whose door he was camped outside. Reluctantly, Bowen agreed. After all, the last thing he needed was the responsibility of a pet.

The cat was still there the next morning. Again Bowen stopped to pet him, eliciting purrs. That’s when he noticed the scratches on the cat’s face and legs, and became even more concerned. Reluctantly, he headed out for another day’s work busking at Covent Garden. When he returned that night, the cat was gone — but in the morning, there he was again in the same spot. Bowen finally knocked on the door. “What cat?” the tenant said. “Nothing to do with me.”

Bowen fed the cat, treated the abscessed wound on his leg, and tried to figure out where he belonged. Concerned about the wound — and about fleas, which had been fatal to a kitten he had as a child — Bowen took his new charge to the nearest RSPCA clinic. He went home with an antibiotic and a couple of weeks’ worth of cat food. The exam, medication, and food cost all the money Bowen had. Still: “I don’t know why, but the responsibility of having him to look after galvanised me a little bit.”

The four-legged half of the duo got a name: Bob, after Killer Bob in the TV series, “Twin Peaks.” Like most young felines, he could go from zero to maniac in seconds, but he took his meds well (an easily pillable cat is something special indeed) and understood everything he was told. Bowen, however, resisted forming too strong a friendship, and after Bob was well he tried to send the cat on his way.

But Bob had chosen Bowen, and of course the cat is the one who does the choosing and adopting. He began to accompany Bowen on his daily busking ventures, trotting along beside him on a lead (or riding on his shoulder, as he charmingly does on the book cover). While Bowen played his guitar, Bob sat nearby or curled up in the case. He was quite a crowd-pleaser. There was an increase in contributions, and some people who frequented the area brought gifts for Bob. Bowen learned the name for “cat” in several languages.

One day, a man’s threatening behavior frightened Bob into running away. Bowen searched frantically, fearing for Bob’s safety in busy London and that perhaps his feline friend really didn’t want to be with him after all. Those fears were dispelled when the two were reunited, thanks to two kind shopkeepers who took the cat in.

The busker with the cat also drew the attention of the local police, and eventually Bowen had to find another line of work. He began selling The Big Issue, a professionally-produced newspaper sold by the homeless, vulnerably housed, and marginalized. (I had never heard of this publication, but it’s heartening to hear of a print publication doing well enough to sustain street sales.)

In addition to all the challenges the two faced on the streets, Bowen nursed Bob through a scary, garbage-induced illness. That helped inspire Bowen to take that final step toward getting completely clean himself: getting off methadone. Bob stayed right by Bowen’s side through the worst of the withdrawal. Bowen realized he had reached a level of recovery and stability he’d never thought possible. Bob became known as The Big Issue Cat.

He and Bowen have become celebrities, with Bob making appearances in hand-knitted scarves and obligingly giving high-fives, and it looks like a sequel and one or two books have followed. By all accounts, though, he remains humble, a ginger tom who loves his human.

You probably won’t see James and Bob busking at Covent Garden these days, but you can find them on Facebook.