(By the way, opposite Newley in the show was Cyril Ritchard, who's best-known to audiences as Captain Hook in Peter Pan with Mary Martin.)
The song is quite well-known, but not in its original form that we have here, and that makes it all the more fascinating to see. For starters, Newley doesn't come on stage as himself, as he could easily have done, singing his Big Hit Song (and it was a hit at the time, as you'll hear from the audience), but as "Cocky," and performs the song in character. While it's full of twists and quirks that people later came to expect from Newley, these come from the character and it certainly makes for a memorable portrayal, as he commits to it completely in a very Newleyesque way.
(Newley was always enamored with mime, and especially Charlie Chaplin. In fact, near the end of his career, he co-wrote and starred in a musical, Chapin, which I saw in Los Angeles. It didn't all work, but had much good in it. Anyway, you'll see a whole lot of Chaplin in this performance.)
But most interesting is visual proof of what I've long had a hard time convincing people of. "Who I Can I Turn To?" has always been sung as a love song -- and an achingly beautiful love song at that. "Who can I turn to, when nobody needs me?" "Who can I turn to if you turn away?" But the thing is...the song isn't a love song at all. Not a love song to a women, not to anyone. The song that Cocky sings comes at one of the lowest points in his life -- he keeps losing The Game repeatedly to the upper-class Sir, and has finally been beaten down one too many times, having his hopes pummeled -- and he performs it to heaven, singing pleadingly to God.
You'll see. You can't miss it.