Even while he was a pupil of the great British cellist William Whitehouse at the Royal College of Music, people noticed that Ivor James had a gift for teaching. Once, when Whitehouse had another engagement, he appointed James to take his class and the remarks were astonishing. Nevertheless, after graduating he went on to a performing career, joining the English String Quartet when composer Frank Bridge was the ensemble's violist.
In 1919, Whitehouse invited him to become his teaching assistant. Again, his talent for teaching became entirely obvious and he soon devoted most of his energies to that field. It is not an exaggeration to say that in Britain it was considered that he began a new age of cello teaching and was a tough teacher. Though quite gentle and tolerant of persons of lesser innate talent, he expected everyone to live up to their abilities. He once wrote in a report, "He seems to keep his brains in his cello bag and forgets to take them out. I want a far higher standard from him."
He stressed an absolutely secure technical foundation, but musically was most concerned with developing an understanding of the ongoing line of a piece of music. He stayed for 34 years at the Royal College. In 1928, he married a former pupil of his, Helen Just, who was by then a fellow professor at the Royal College and member of the English String Quartet (which he had left several years earlier). The year after that, they worked at establishing a summer course of study specializing in music. This hardly seems a radical thing now, but James was the first in England. It was held in 1928 at Westminster College, Cambridge, and is the inspiration for many summer music programs.
In addition to teaching cello, he taught chamber music. In the days of the German bombing of London, the precious paintings at the National Gallery in London were moved out for safekeeping and pianist Dame Myra Hess organized lunchtime concerts there, which so helped morale that they were credited with "keeping people sane." One of the most celebrated parts of that series was the illustrated lectures he gave on the late Beethoven string quartets. He became the grand old man of the cello in England and continued teaching until two months before he died at the age of 80.