Compare George Smiley and James Bond.

Whereas Ian Fleming's dapper James Bond is a latter-day symbol of the stereotypical British hero of the glory days of empire, George Smiley might be said to symbolize the British Empire in a state of appallingly precipitous decline. Bond is handsome, athletic, socially versatile, extroverted, and irresistible to gorgeous, sexy, exotic women all around the world. Smiley, on the other hand, is short and pudgy. He buys good clothes but always looks wrong in them. His wife Anne once told him he looked like a big tea cosy. He is shy, awkward, introspective, bookish, cautious, nothing at all like a dashing secret agent. He hardly knows how to handle a gun, and he ruins the excellent silk lining of his jacket when he keeps an oily automatic in his pocket. Far from being irresistible to the ladies, he has a wife who is so profoundly unfaithful to him that her promiscuity is notorious.
James Bond and George Smiley have virtually nothing in common except their devotion to duty. Smiley is never in danger, although he lived in constant danger as an undercover agent in Germany during World War II. Bond is always in danger and thrives on it. It seems unlikely that many people would enjoy reading about both James Bond and George Smiley. Bond is a man of action. George is cerebral. Bond drives the fastest cars and handles the latest spyware with confidence and dexterity. Smiley is totally inept with any kind of machinery or gadgetry. He has a terrible time wrapping a package with Scotch tape. He spends hours trying to make a print from a negative. He hates driving a car and takes taxis whenever he can; but when he has to rent an Opel in Germany to visit Otto Leipzig, the car gets so badly damaged that he is afraid to return it to the agency and leaves it in a public garage. James Bond is the last vestige of the derring-do that built the British Empire on which the sun never set. George Smiley is the hapless hero trying to cope with the two new superpowers on the world stage, the Soviet Union and the United States of America.
When Smiley goes to Saul Enderby for authorization and financing to set a trap for Karla, Enderby says:

"And it's not all a wicked Bolshie plot, George, to lure us to our ultimate destruction--you're sure of that?"
"I'm afraid we're no longer worth the candle, Saul," Smiley said, with an apologetic smile.
Enderby did not care to be reminded of the limitations of British grandeur, and for a moment his mouth set into a sour grimace.

Connie Sachs sees the big picture too. In Tinker, Tailor, Soldier, Spy, she tells Smiley:

"Poor loves. Trained to Empire, trained to rule the waves. All gone. All taken away. Bye-bye world. You're the last, George, you and Bill."

And Bill Haydon turns out to be the mole Smiley has been asked to unearth, making George Smiley the last man standing.