LONDON — Before her successful, if somewhat niche, career, the Hungarian-born pearl stringer Renata Terjeki was never a fan of pearls.

“I never wanted to string,” said Ms. Terjeki, 47, in a recent video interview from her small, windowless, lamp-lit workshop, tucked in the basement of the luxury antique jeweler Bentley & Skinner on London’s bustling Piccadilly.

To her mind, pearl necklaces were the preserve of people over 80, and stringing was an easy pursuit: “I assumed all they do is just chuck the pearls on a string, tie it somehow, and that’s it,” she said.

But the variety and complexity of her work over her 15-year career has proved otherwise.

Today, Ms. Terjeki is entrusted with some of the world’s most exquisite pearl jewelry, to be restrung, repaired and occasionally redesigned.

Discretion “is an unspoken rule in the trade,” said Ms. Terjeki, who is often required to sign confidentiality agreements when working on high-end pieces. But clients she can name include the auction houses Bonhams and Sotheby’s, and the jewelry emporiums Moussaieff and Bentley & Skinner. Private clients have included a daughter of the Russian president, Vladimir V. Putin, (for whom she strung a prayer-bead-like gold and pearl necklace one Christmas), and European royalty.

Almost all find her via word of mouth.

In 2015, Ms. Terjeki, opened an Instagram account under the moniker @stringing_along. She wanted to correct the misconceptions around pearl stringing that she herself had harbored. Among the works on display there are woven pearl watch straps, black diamond loafer tassels, gemstone curtain ornaments and an antique Cartier bag covered in tiny pearls.

Contrary to what one might expect, precious and semiprecious stone beads, and occasionally even coral, make up an estimated 35 to 40 percent of Ms. Terjeki’s work, she said. (“It’s the same technique,” she said. “Just a different material.”) And even ribbon is part of her repertoire. It is traditionally a pearl stringer’s job to wind velvet, hair-colored ribbons about the frames of some tiaras, she said.

To date, her Instagram feed has more than 17,000 followers, some no doubt drawn by the profession’s unusual nature: Expert pearl stringers are hard to come by.

“She is one of a dwindling number of independent practitioners keeping alive this valuable skill,” said Emily Barber, director of jewelry at Bonhams UK — an auction house that has worked with Ms. Terjeki for 12 years. (“Renata is the doyenne of pearl stringers,” she said.)

Ms. Terjeki estimates there are only a handful of high-level pearl stringers left in London.

This scarcity is likely the result of a shift away from the regular wearing of expensive, natural pearls, said Kristian Spofforth, head of department, Sotheby’s jewelry, London. In the early 20th century, when natural pearls were at their peak, “it’s something you got done regularly,” he said. In this day and age, he said, more people are wearing cultured pearls or less valuable pearls.

“Perfecting it and doing it well is remarkably difficult,” he said of the work.

Ms. Terjeki came upon the profession by chance, when a veteran stringer offered her an apprenticeship, and in part credits her success to her background as a goldsmith.

In Budapest, she studied under a master goldsmith, Rezso Ludvig, an artist well known within Hungarian jewelry circles for restoring the Hungarian crown jewels, she said. His insistence that all students learn to craft everything by hand using only the most basic tools can be seen in her work today.

Though specialist tools exist, her own are simple. And, except for her drill and mannequin, all fit into a wooden box she carries with her when the value of a piece means she’s required to string elsewhere.

Among the few items arranged inside, said Ms. Terjeki, can be found a “gimp” — a tiny coil of metal that prevents the pearl from rubbing against the clasp, a 0.23-millimeter needle — the slimmest available — for threading, and a section of a red cotton table runner brought from a housewares store. (The color allows her to see the pearls clearly, and the fabric “has little grooves, which stops the pearls rolling,” she said.) Knots are tied with an “ordinary” needle that slots into a rounded wooden handle, she said. And as for her thread, though some use silk, Ms. Terjeki favors nylon: Unlike silk, nylon “is durable, so the knot stays nice and neat,” she said.

Though she declined to give a base price because of the many variables (principally whether the client is trade or private, the value of the piece and the time it will take), her work ranges widely in cost and complexity.

At one end of the scale are single-row necklaces. At the other are plaited sautoirs — the French name for long necklaces formed of woven ropes of pearls with wires crisscrossing inside that often culminate in one or more tassels. As the work can require up to 10 hours a day of complete concentration for three weeks to a month, she said, the cost can rise to a few thousand pounds.

In addition to its intricacy, the time spent on a sautoir can depend on the size of its pearls.

“Sometimes the pearl hole, and the pearl itself, is so tiny even my thinnest needle won’t go through,” Ms. Terjeki said.

Her solution: Split the nylon thread into its component strands and, taking the slimmest, harden it with a minuscule dab of strong glue and slide it through the pearls like a needle. That’s why she is nearsighted, she said. “I don’t need glasses for work, but I do need glasses for driving, watching a movie, because I stare at everything so close all day long.”

Time restrictions and the value of a piece can add to the sometime high-pressure nature of her job, said Ms. Terjeki, who was once required to complete a five-row natural pearl necklace worth over £1 million in only two hours while seated beside a bodyguard in the SSEF pearl lab in Zurich.

“With a 17th-century necklace, I can’t just go and get another one,” she said.

But this gives the job its appeal.

“I like challenges,” said Ms. Terjeki, whose maxim is “nothing is impossible” and who has no plans to retire.

Today, pearl stringing is her passion, she said. “I don’t know if I could live without it.”