Lightfoot was one of the original members of the Westminster Assembly; his "Journal of the Proceedings of the Assembly of Divines from January 1, 1643 to December 31, 1644" is a valuable historical source for the brief period to which it relates.
Lightfoot adalah salah satu anggota asal Westminster Assembly; karyanya "Journal Proceedings of the Assembly of Divines from January 1, 1643 to December 31, 1644" adalah sumber sejarah berharga untuk periode singkat yang dicatatnya.