In 1869 he became a partner but decided to leave and pursue a university education, entering Downing College, Cambridge in 1871.
His career at university was particularly brilliant; in 1872 he was awarded a scholarship, in 1874 he was senior in the law and history tripos, won the Winchester Reading Prize, and was elected president of the union.
[3] Kenny was elected a fellow of Downing College in 1875 and was appointed to a lecturership in law and moral science.
In 1881 Kenny was called to the bar at Lincoln's Inn and joined the south-eastern circuit.
In 1907 he was elected to replace the recently deceased Frederic William Maitland as Downing Professor of the Laws of England, a position he held until his retirement in 1918.