Over the end credits the soundtrack is the "Boom-ooh-yatatatah" sketch seen on stage in the first episode. However, this is not the re-enactment from the first episode, but the actual recording from the television performance of the sketch by the real Eric Morecambe and Ernie Wise, from the series Two of a Kind (1961).
The show offers up a mostly laudatory picture of Nicholas Elliott, with the end titles saying that his reputation remained intact. In fact, while Elliott was exonerated of any possible collusion with the Soviets, a number of people, including Ben McIntyre, who wrote the book on which the series is based, believe that Elliott intentionally allowed Philby to escape in order to avoid a trial which would have been embarrassing to the old boys' network of MI6.
The ending seems to portray Angleton's paranoia about moles as resulting entirely from his relationship with Philby. It even seems to suggest that his turn towards mole hunts may have been an attempt to cover up for his own failure to detect Philby's betrayal. In reality Angleton's paranoia was more general and had a number of sources including KGB defector Anatoliy Golitsyn, who defected a few years before Philby's betrayal was discovered, and who helped convince Angleton of widespread Soviet penetration of western intelligence services.