An annotated page from “A Bear Called Paddington,” illustrated by Peggy Fortnum. (Dan Kitwood/Getty Images)

Peggy Fortnum, a British illustrator whose winsome, whimsical drawings brought Paddington Bear to life in 1958 and have delighted young readers around the world ever since, died March 28 at a nursing home in Colchester, England. She was 96.

She had dementia, said a nephew, film scholar Kevin Brownlow.

Generations of youngsters have learned to read, whiled away rainy afternoons and drifted off to sleep in the company of Paddington, one of the best-known and best-loved members of the abundant ursine population in children’s literature.

He was the creation of Michael Bond, a BBC cameraman who stumbled into a London department store on Christmas Eve in 1956 and purchased a lonesome-looking teddy bear as a last-minute gift for his wife.

A writer on the side, Bond imagined a scenario that might have brought a bear to the United Kingdom: The creature was an orphaned immigrant from “darkest Peru,” sent to England as a stowaway by an aunt admitted to a home for retired bears in Lima. He wrote the tale in a book published two years later as “A Bear Called Paddington.”

The “Paddington” books, first illustrated by Peggy Fortnum, above, sold tens of millions of copies and were translated into dozens of languages. (Family photo)

Ms. Fortnum, already an seasoned illustrator, was commissioned to do the artwork.

The Paddington book grew into a Paddington series that sold millions of copies in dozens of languages, joining A.A. Milne’s “Winnie-the-Pooh,” Else Holmelund Minarik’s “Little Bear” and Stan and Jan Berenstain’s “Berenstain Bears” books in the category of literary classics featuring bears.

Few readers, young or old, who have thumbed the pages of a Paddington book can think of the bear without picturing Ms. Fortnum’s illustrations, which she developed after visits to the London Zoo. The paws, she said, presented a particular challenge.

“He had to look real,” she wrote in unpublished memoirs transcribed by her nephew. “People who saw him had to believe in him just as they believe in Winnie-the-Pooh. But he just happened. I had bearish qualities in my mind, but he just arrived in my imagination.”

For readers, the bear arrived, after a long trip across the Atlantic, at the Paddington railway station in central London, where he was rescued and where he got his name. A kindly English couple, Mr. and Mrs. Brown, spot him on the platform and notice the message on his suitcase: “Please look after this bear. Thank you.”

Overcome by equal parts pity and curiosity, they take him home to their family, promising him daily servings of marmalade — his favorite food — and honey on Sundays.

In her original pen-and-ink drawings, Ms. Fortnum depicted Paddington with a floppy hat and duffel coat. With a few strokes of a pen, she could send him flying on a bicycle or direct his eyes up or down to betray a universe of emotions.

“Her line is exquisite in its loose and nervous rhythm; she can create movement with what, out of context, would be a meaningless squiggle; she can suggest by a few doodles a storm-clouded sky or the hidden recesses of a candlelit room,” a reviewer wrote in the Times Literary Supplement, according to Ms. Fortnum’s obituary in Britain’s Guardian newspaper.

Years after they appeared, some of Ms. Fortnum’s drawings were colored in by artists including her niece, Caroline Nuttal-Smith. Paddington’s coat became blue, and his hat became red.

In color as in black and white, the drawings conveyed Paddington’s clumsiness and yet his dignity. It was noted that Paddington was a refu­gee — a fact not lost on the book’s first readers, who were born during or in the aftermath of World War II, and that gave the young bear enduring resonance as the decades wore on.

The Paddington franchise grew to include board books, stuffed animals, and television and movie adaptations. By virtue of its durability — the most recent title, “Love from Paddington,” was published in 2014 — the book series employed several illustrators after Ms. Fortnum, among them Fred Banbery, David McKee and R.W. Alley.

Ms. Fortnum’s original drawings are regarded as valuable collectors’ items and can fetch thousands of pounds at sale — a tangible measure, perhaps, of the intangible nostalgia that they inspire among formerly young readers.

Margaret Emily Noel Fortnum was born in Harrow on the Hill, an affluent area of London, on Dec. 23, 1919. She didn’t do well in school but loved to draw.

She abandoned her early artistic training to join the Auxiliary Territorial Service, the women’s branch of the British army, during World War II. She was severely injured when she fell out of a troop carrier and was run over by a truck, returning to her studies only after a long period of convalescence.

At a London art school, Ms. Fortnum befriended Judith Kerr, who had escaped Nazi Germany and would later write children’s classics including “When Hitler Stole Pink Rabbit.”

In school, Ms. Fortnum wrote, she learned that “one should try and get inside the character one was drawing, even if it was only a doll.” Her first illustrations were for the book “Dorcas the Wooden Doll” by Mary F. Moore.

Mrs. Fortnum later illustrated works by Kenneth Grahame, the author of “The Wind in the Willows,” and Noel Streatfeild and Jane Gardam. Arthritis eventually forced her to retire.

Ms. Fortnum’s husband of three decades, Ralph Nuttall-Smith, died in 1988. She had no immediate survivors.

In her unpublished memoirs, Ms. Fortnum recalled that when she first read the manuscript of “A Bear Called Paddington,” she “laughed all the way through — there were tears in my eyes.”

“I believed in Paddington — I believed he really existed,” she wrote. “I felt a bit like this animal myself.”