He then co-wrote, with Matthews, a paper On the reduction of arithmetical binary cubics which have a negative determinant: it was published after Berwick had left Cambridge to take up an assistant lectureship at the University of Bristol, and was the only paper Berwick co-authored in his career.
In 1926, with thirteen research papers to his name, Berwick returned to Bangor to serve as Chairman of Mathematics.
In 1927 he published Integral Bases, an ambitious account that used heavy numerical computations in place of practical proofs.
[citation needed] Berwick was described as a tall man with a distinctive voice and forthright personal style.
He had a keen interest in teaching, publishing a number of mathematical recreation articles and giving several addresses at meetings of the British Association.