Penston was demonstrator in
Botany at Oxford in 1928–29. She then moved to
King's College London, where she was assistant lecturer from 1933 to 1936 and lecturer from 1936 to 1945. In 1945 she became the first woman to be vice-principal of
Wye College, part of the
University of London, following its amalgamation with
Swanley Horticultural College. Throughout her career she maintained teaching responsibilities, lecturing on mineral nutrition of plants and plant anatomy. Penston was a member of the Senate of the University of London and on the council of several academic institutions. She was unmarried, and died on 1 February 1974. ==References==