During the
Interregnum Armstrong was a supporter of
Charles II, participating in the plot to seize
Chester Castle in 1655, and carrying funds from
Aubrey de Vere, 20th Earl of Oxford to Charles in exile. He was possibly imprisoned for a year on his return. In 1657, he married Catherine, daughter of James Pollexfen and niece of
Edward Hyde, 1st Earl of Clarendon. , 1684 Following the
Restoration, he received, in February 1661, a commission as
captain-lieutenant in the
Royal Horse Guards. In August 1675, Armstrong killed the son of one of the queen's ladies-in-waiting at a London theatre. Armstrong was pardoned on the grounds that his opponent had drawn first. Armstrong served with
James Scott, 1st Duke of Monmouth in France from 1672, fighting at the
Siege of Maastricht (1673) and alongside the Dutch, in 1678. He was wounded at
St Denis. In 1679, he helped suppress the covenanter rising and fought at the
battle of Bothwell Bridge, at the same time that the
Popish Plot in England was scaring the Anglican establishment. Monmouth's influence secured him as MP for
Stafford in March 1679 to the
First Exclusion Parliament. == Death ==