Occasionally an anthology episode appears to be poorly rated partly because the main character is outrageous or absurd, although well delineated, and the dialogue may have some merit. Have a Nice Death, with Simon Cadell playing an outspoken misogynist author, is a possible example.
The Best Policy does not fall into this category. I've recently watched all 112 episodes, and this the most abysmal, beating some keen competition. Harry Flock (Gary Burghoff) is a bank clerk, physically unappealing and with most horrible high pitched whining voice. The entire story is just one long moan from Harry, who feels the world does not sufficiently appreciate him. "My books are impeccable", "why am I being subjected to this", "someone's trying to sabotage me" wails the hapless Harry. Indeed, he even makes his namesake Prince Harry look happy by comparison.
I can't recall why but near the end Harry's boss exclaims "I've just been through the most gruelling experience". Anyone sitting through this dire episode will sympathise.