[citation needed] On stage he has played leading roles in most of the UK's regional theatres including Birmingham Rep., Nottingham Playhouse and the Bristol Old Vic where parts ranged from Mamet to Molière.
As a member of the Royal Shakespeare Company he worked in Stratford and London and has performed in the West End in plays by Noël Coward, Tom Stoppard, Agatha Christie and most recently in Yes, Prime Minister (2013).
Armstrong's television credits include: Z-Cars, Doctor Who (in the serial The Masque of Mandragora), Blake's 7, The Professionals, Terry and June, One Foot in the Grave, Casualty and EastEnders and Birds of a Feather.
[citation needed] The play has won awards in New Zealand, Canada, Spain and Germany and been translated into Catalan, Spanish, Italian, French and Russian as well being performed on Dutch television and Romanian radio.
[citation needed] In 2015, Armstrong wrote a five-handed comedy called Fondly Remembered which premiered in London, and was subsequently published by French's Acting Editions.
[citation needed] Armstrong has lectured and taught on campuses across the US and taken workshops and masterclasses in India, Sri Lanka, New Zealand, Italy and all over the UK.