Armyne, a younger son of the prominent puritan Armyne family of Osgodby, followed his eldest brother to Cambridge, before going on to pursue a legal career at Gray’s Inn. With his brother’s support he was returned for Grantham in 1626. He took no known part in the second Caroline Parliament and never sat again. His marriage brought him a small estate in Rutland, valued at between £150 and £200 a year, where he subsequently resided and was appointed to the local magistrates’ bench and other offices.
During the Civil War Armyne lived in London until March 1644 when, as a deputy lieutenant of Rutland, he raised two troops of horse for Parliament and assumed responsibility for the sequestration of the extensive royalist estates in the county.
