a Buster Keaton tribute as Hay and Hulbert end up hanging off the clock face of Big Ben
It sounds like it was actually a tribute to Harold Lloyd. The famous clock face routine is in his film Safety Last.
(To confirm my recollection, I searched Google for "buster keaton clock". Oddly, the first page of results contains four images from the Harold Lloyd film, a YouTube link for the Harold Lloyd film, a Wikipedia article about the Harold Lloyd film, and five other links related to the Harold Lloyd film. The interwebs seem to think Buster Keaton and Harold Lloyd were the same person.)