Complex sentence: On his return to the UK, Sweeney "drifted into publishing" acted as commissioning editor in commercial book and journal publishing, initially at the Pergamon Press and then at Basil Blackwell International Arts and Humanities Publishers.
Split into simpler sentences: On his return to the UK, Sweeney "drifted into publishing". He acted as commissioning editor in commercial book and journal publishing, initially at the Pergamon Press and then at Basil Blackwell International Arts and Humanities Publishers.