Film roles included Maurice Braithwaite in This Sporting Life (1963), Vahlin in The Long Ships, Dr. Watson to Robert Stephens's Holmes in The Private Life of Sherlock Holmes (1970), and Joseph Stalin in Jack Gold's Red Monarch (1983). In the 1975 British film, It Shouldn't Happen to a Vet, derived from the James Herriot books, Blakely played the eccentric Siegfried Farnon. He also appeared in A Man for All Seasons (1966), Young Winston (1972), The National Health (1973), Murder on the Orient Express (1974), The Pink Panther Strikes Again (1976), Equus (1977), The Dogs of War (1980), Nijinsky (1980) and Evil Under the Sun (1982).