he was made a judge in 1547, and knighted by king edward vi. when richard rich, later 1st baron rich was ill, portman was one of those who, by letters patent of 26 october 1551, were commissioned to despatch chancery matters; and in the following january he was commissioned to aid the lord keeper of the great seal, thomas goodrich, bishop of ely, in similar affairs. he seems to have been reluctant to adopt the new protestant religion, and found no difficulty in keeping office under the catholic queen mary. he followed day, the bishop of chichester, in persuading sir james hales to abjure protestantism in 1554. the same year he was made lord chief justice of england and wales. he died early in 1556-7, and was buried, with a stately funeral, on 10 february 1556-7 at st dunstan-in-the-west, london.