Complex sentence: After a research fellowship and temporary lectureship at Manchester, he obtained a permanent position at The Open University in 1975, staying there until retirement in 2015, when he became Emeritus Professor of Education and Social Research.
Split into simpler sentences: After a research fellowship and temporary lectureship at Manchester, he obtained a permanent position at The Open University in 1975. He remained at the Open University until retirement in 2015, when he became Emeritus Professor of Education and Social Research.