having turned down an offer in 1947 to return to his old employer, trinidad leaseholds, in 1954 constantine agreed to join the same company as an assistant legal advisor. uncertain about going back to trinidad after living for 25 years in england, he nevertheless believed it was a good time to return, particularly as his daughter was moving there to marry. before leaving england, he published his book "colour bar" (1954), which addressed race relations in britain and the racism he had experienced. it also discussed worldwide racial oppression and how the lives of black people could be improved. at the time, according to peter mason, this was "an explosive, challenging, hard hitting tome, the more so because it came not from a known black militant but from someone who seemed so charming, so unruffled, so suited to british society". although not viewed as radical by black audiences, it was aimed at white british readers. the british press gave it mixed reviews and criticised him for unfairness in parts of the book; other critics accused him of communist sympathies.