Armstrong is known for his role as Brian Lane in the BBC One series New Tricks about a group of former police detectives who help investigate unsolved and open cases for London's Metropolitan Police.
Armstrong dikenal karena perannya sebagai Brian Lane di BBC One series Trik Baru tentang sekelompok mantan detektif polisi yang membantu menyelidiki kasus yang belum terpecahkan dan terbuka untuk Polisi Metropolitan London.