It's hard to believe that there were only ever twenty episodes of this classic British comedy ever made. Ronnie Barker ("Fletch") is fantastic as the habitual criminal sent to Her Majesty's Prison "Slade" - perched in the northern reaches of England - for five years. His cellmate is the honest, but supremely naive "Godber" (Richard Becksinsale) and the series depicts their antics surviving the authoritarian regime of "Mr. Mackay" (the outstanding Fulton Mackay) in his uniform, and "Grouty" (the comically menacing Peter Vaughan) on the inside. Dick Clement and Ian la Frenais have created a…