Constantine arrived in England with the West Indian touring side of 1928 and stayed. Nelson, a small Lancashire mill town, had begun signing overseas professionals in 1922; in 1929 they offered Constantine £500 per season — more than the Trinidad oilfields where he had been a clerk, more than any West Indian cricketer of the day could earn from Tests. He accepted.
He was, statistically, the most dominant overseas pro the Lancashire League had ever seen. His all-round figures — wickets at under 10 each, batting average in the high 30s, fielding so spectacular that local papers ran weekly diary columns of his catches — pulled crowds across class lines. Saturday gates at Seedhill rose from 2,000 in 1928 to over 6,000 by 1934. Nelson won the league in 1930, 1931, 1932, 1933, 1934, 1936 and 1937.
Constantine used his earnings to study law part-time; he qualified as a barrister in 1954. He also became the first black author of a sustained body of cricket writing, and a public voice on race relations in pre-war Britain. He was refused service at the Imperial Hotel in London in 1943 — an incident that resulted in a 1944 court judgement ('Constantine v Imperial London Hotels') still cited as one of the foundational anti-discrimination cases in English law.
In cricket terms, the Lancashire League decade also limited his Test career: he was unavailable for several West Indian tours because Nelson contracts paid more. He played only 18 Tests in 11 years.