Even at a time when comics could expect to sell more copies, and survive longer, its still an impressive longevity which I doubt few titles could ever hope to achieve today (although the accumulated totals of the Panini SPIDER-MAN and X-MEN Collectors' Editions, both launched in 1995, are nothing to be sniffed at).
The celebrations would have happened a few weeks earlier had publication and distribution of the weekly not been disrupted by industrial action in the haulage industry in early 1979.
The British weekly eventually notched-up 666 issues before succumbing to falling sales and sporadic distribution (copies were often impossible to find and I had to place "a regular order with my newsagent" to ensure my weekly dose) in December 1985. A further 51 weeks were added to the cumulative total, in the form of SPIDER-MAN AND ZOIDS, in 1986-87 before the web-slinger's British reprints went on hiatus.
Issue 500 was the first to appear under the simple "Spider-man" masthead, despite the house ad that retained the previous "Super Spider-Man TV Comic' logo, a legacy from the 1981 tie-in with the live-action TV show.
The anniversary issue also absorbed THE INCREDIBLE HULK. A case of history repeating itself as the Green Goliath's first British solo title had also sought the web-head's sanctuary in 1980.
The special occasion was marked by this impressive wrap-around rouges gallery cover and free cover-mounted badge (my copy has long-since lost the freebie... and sustained some battle damage in the process). The glossy centre pages made the most of the merger with this original pull-out Hulk/ Spidey "team-up" poster with a suitably insane-looking Hulkster.