Originally destined to be a research chemist, Halcox took a trainee laboratory job at Glaxo, and began to study for his exams while pursuing his nascent interest in jazz. He had stumbled on traditional jazz when a record shop counter-hand played him a King Oliver record; he soon fell in with other like-minded enthusiasts. Having started on piano, the Briton transferred his allegiance to the trombone while in the RAF, but when his local friends needed a trumpeter for their amateur band, he changed instruments again, this time permanently. "I thought I'm not going to be left out," he said. "The trumpet wasn't a difficult leap in those early days."
Balancing his growing passion for jazz with his day job he also played football and hockey for Glaxo proved to be more of a challenge. As he crammed in as many jazz sessions as he could, he began to fall behind in his studies. "I wasn't getting through any exams and before you know where you are, the music becomes the most important thing to you."
Early on, Pat had wedded himself to the strict New Orleans style; later, he broadened his tastes as the ensemble widened its repertoire and toured with key players from the heyday of U.S. mainstream jazz. Barber's deep understanding of blues and gospel also brought the group into contact with Muddy Waters (they sat in with the bluesman at his Chicago South Side club) and Sister Rosetta Tharpe.
Barbers band provided the soundtrack music for the 1959 film version of John Osbornes Look Back in Anger. Jimmy Porter, the plays anti-hero, is a would-be jazz trumpeter, played in the film by Richard Burton. It fell to Halcox not only to dub Burtons trumpet playing, but also to teach him how to mime the part realistically.
In 1977, when Barber took a summer break, Pat formed his own All Star Band. Another passion in the musician's life was photography and his work is in many of the group's programmes.
As the performers began to spend more time touring in Europe they were especially popular in Germany the travelling took its toll and at the age of 78 Halcox retired. Even so, he continued to play and front occasional bands of friends and sometimes returned to guest with Barber.
A cause of death was not revealed.
Halcox is survived by his wife, Shirley, and their son, Julian.