LONDON — While Joe and Charlie Casely-Hayford have been expanding their fashion company have been expanding their successful men’s and women’s wear lines, the father and son have remained devoted to one watch brand: Breitling.

Charlie Casely-Hayford, 29, who designs many of the company’s clothes and also has modeled for Converse and Dr. Martens, prefers the Breitling Navitimer 01.

“When I was growing up, my dad always wore a smaller Breitling, and it had a big impact on me,” Charlie said recently by phone from his East London atelier. “It was the one thing that was consistent that he wore.”

“But the larger Navitimer works better for me — mostly because I’m 6-foot-6 and partially blind,” he added with a laugh.

It’s also a matter of keeping things simple. “I wear pretty much the same thing every day. I’m not a hoarder. I don’t acquire a lot of things, so what I do acquire becomes standard,” he said. “I like the permanence of something I can always fall back on, because the fashion industry is fast-paced and transient. It allows me that moment to catch my breath.”

The father and son are unpaid ambassadors for the brand. And for Joe Casely-Hayford, formerly the creative director of Savile Row’s Gieves & Hawkes, Breitling was where it all began. In 1991, he bought a Breitling Navitimer Cosmonaute watch, the same model that was worn by a Russian cosmonaut on, coincidentally, Joe’s sixth birthday — May 24, 1962.

“I really love the Breitling design from a functional point of view,” Joe said by phone recently. “I like the functional masculine watches.”

He carried that idea into his more recent purchases, all the while staying with Breitling as the family business boomed. “In 2012, I bought a Chronomat limited-edition, which is a real chunky monster and quite a statement piece,” he said. “I’ve always thought a good watch is the key to a man’s wardrobe. I have quite a wide range of watches. Come to think of it, I have more shoes than my wife.”