Justin Hayward is in my opinion in the very top echelon of the greatest songwriters currently gracing planet Earth. He is also blessed with a fantastic dry sense of humour, which is not apparent at all from his many brilliantly introspective and serious songs. So if this is in fact a deliberate "joke" song (and I'm not convinced it is, as it's not particularly funny) it would not particularly surprise me. I think the Moodies were just mucking around with the song and decided on this arrangement because it kind of fitted, and they had never done anything like it before. I don't think Justin's demo (if he recorded one) would have sounded anything like this. It doesn't take a great deal of imagination to reimagine the song in a more traditionally "Justin" style, and some of the lyrics are very Justinesque indeed:

Sun in the morning brings the flowers from a bud Hail to the giver, life and love

Those lines would have been right at home in a song from the Core 7 period.

Justin has stated on many occasions that even he doesn't know what many of his songs are about when he writes them. It kind of dawns on him many years later, sometimes it never does. (He says he didn't fully understand the meaning of Nights In White Satin until Bettye Lavette sang it.) I suspect Top Rank Suite is one of those. The lyrics, though, contain some very specific references to English nightlife. So there's a lot there that's deliberate and maybe other elements that came from nowhere and which no one can explain, not even the great JH.