Supervised by Tom Harris, she was awarded her PhD in 1941 by the University of Reading for her thesis titled 'An investigation of some problems of freshwater algae, with special reference to the process of sedimentation'.

[2] In the same year she, along with colleagues at the FBA, published the landmark paper 'The Study of Lake Deposits' in the academic journal Nature.

[3] Whilst attending Easter courses at the Freshwater Biological Association (FBA) near Lake Windemere Pennington met Limnologist Clifford H. Mortimer and plant ecologist William Pearsall, both of whom were to have major influences on her subsequent research.

[4][5] After a period working at the FBA in Windermere and at the then Botany School in Cambridge Pennington went on to become one of a new generation of respected women researchers.

[7] Her final years were spent in the village of Kingsclere where she remained actively involved in research, co-authoring important papers until 2003.