 Working as a record agent and translator, Illingworth entered Gray's Inn on 25 June 1825, but was not called to the bar.He had hopes of becoming a sub-commissioner to the sixth Record Commission, and in May 1831 drew up a set of "Observations on the Public Records of the Four Courts at Westminster, and on the measures recommended by the Committee of the House of Commons in 1800 for rendering them more accessible to the public", for the private use of the commissioners