In 1966, the Prime Minister, Harold Wilson, invited Blanch to succeed Clifford Martin as Bishop of Liverpool. On opening Wilson's letter Blanch is said to have taken it for a prank by Rochester students. He was not altogether pleased by the offer. Because he had acquired his faith not from churchgoing but from his private reading of the New Testament, he was, in the words of "The Independent", "uncoloured and uninfluenced by anything ecclesiastical and failed to see the relevance of much of it." The prospect of exchanging academic life for the complexities of a bishop's duties was daunting. "The Times" later said, "He was at that time a bad chairman of committees and councils (he got better at it) and he knew there would be plenty of both. He did not know Lancashire. But he knew his duty and off he went to Merseyside." Aged 47 he was the youngest Anglican bishop of his day.