David Mitton, a creator of the gentle children’s television series “Thomas the Tank Engine and Friends,” which evolved into an international hit and a merchandising juggernaut, died on May 16 in London. He was 69.

His death was announced May 28. The cause was a heart attack, said Michele Fabian-Jones, one of Mitton’s partners in Pineapple Squared Entertainment, a children’s television production company.

Mitton, a veteran of British children’s programming, directed or wrote more than 180 episodes of “Thomas the Tank Engine,” beginning with the first one in October 1984. The series, originally called “Thomas the Tank Engine and Friends” and later shortened to “Thomas and Friends,” became an instant success on British television and in 1989 made its debut in the United States as “Shining Time Station” on PBS, with Ringo Starr in the role of Mr. Conductor. (George Carlin took over the role after one season.)

Like their British counterparts, American viewers fell in love with the put-upon but determined Thomas, described in the show’s first episode as “a cheeky little engine.”

Thomas, a bright-blue engine with a round face and big eyes, found adventure and life lessons on the mythical Island of Sodor with a team of engines that included the big, self-important Gordon, wise Edward, uppity James and pesky young Percy. Together, they learned the values of friendship, teamwork, honesty and kindness to others.

The series became an unstoppable phenomenon that continued to gather steam, so to speak, long after its original creators had moved on to other projects. Now seen in 145 countries, it supports a vast empire of tie-ins that include books, video games, toys, and clothing.