I suppose I can hardly count such a famous actor as unknown, but the reassuringly wholesome rumpled features of Frank Windsor have been seen more widely than just in the venerable cop dramas 'Z-Cars' and 'Softly Softly; Taskforce' or adverts for pension plans and stairlifts. Starting as an actor in the late '50s, he never played the dashing leading man, but more often the trusty retainer or honest yeoman. TV jobs include the sci-fi serial 'A for Andromeda', 'The Avengers', 'Randall & Hopkirk, Deceased', the title role in the series 'Headmaster', and the not very memorable limo-hire drama 'Flying Lady'. More recent appearances cover the usual suspects 'Boon', 'Casualty', 'Chancer', 'Midsomer Murders', 'Judge John Deeds' and so on.
On the big screen he is far less ubiquitous, but pops up in favourites like 'This Sporting Life' (1963), 'Spring and Port Wine ' (1971) and 'Sunday Bloody Sunday' (1971), as well as duffers such as 'Barry McKenzie Holds His Own' (1974), and heist romp 'The Omega Connection/The London Connection' (1979), often pastiching his copper persona.
Dependable rather than riveting. Hence the insurance adverts.