In 1951 he had been appointed deputy director and keeper of art at the Belfast Museum and Art Gallery but in 1957, Hewitt left to take up the position of Art Director at the Herbert Art Gallery and Museum in Coventry, a position he held until 1972.
Hewitt's career path involved serving as deputy director and art curator at the Belfast Museum and Art Gallery from 1951 to 1957, after which he became Art Director at the Herbert Art Gallery and Museum in Coventry until 1972.