This was Slade's 3rd number one chart-topper, spending 3 weeks at the top in 1972, and was their second number one of that year. Source.
12 years ago Slade had their 20th anniversary.
I'm not sure if things have changed that much since then. Of course, Noddy is no longer in the band's line-up. The charts are pretty much dead, replaced by iTunes or whatever online source of information new bands aspire to. Hopefully, good, passionate music still comes to the fore, and that bands with character still come to the heart of the country enough to have the mickey taken from them in a loving way.
Next time you hear the strains of "it's Christmassssss" give a thought to Slade, and the inspiration that they were to others.