AJ Black’s review published on Letterboxd :
If you ask anyone about Diamonds Are Forever, I would wager they can only remember two things: that Sean Connery played James Bond and Shirley Bassey's fantastic theme tune. Oh and the fact diamonds are involved, naturally. Will they recall the plot or characters? I doubt it. I had forgotten much about Connery's last official appearance as Bond and with good reason it turns out; this is, easily, the worst of the franchise yet and I would argue indeed one of the poorest ever seen. It's just ill-conceived on numerous levels, trying so hard to recreate Connery's greatest hits as the character and failing badly, for the most part.
It's perhaps too honouring of Ian Fleming's source material, as anyone who read his books know they don't often track, plot wise, with a traditional Bond movie feel. The whole thing at times just doesn't feel like a Bond adventure, more like an OTT detective story that would have been more suited to an American leading character; the American influence on the story & script is wholesale and Bond is far less interesting a franchise when he's being chased by US gangsters or idiotic cops, which he is for much of this. The exotica of Las Vegas is there but it soon becomes watered down by a quite bizarre plot that after a low-key smuggling build-up soon expands into orbital laser beams and Capricorn One-style faked moon landings - the two just fail to sit right with each other. The other issue is Connery; he's never looked more like he's just taking the money and running, served by a flat script he can do little with (bar a couple of classically executed lines) but I'm not surprised he ducked out after this - it's his least assured, least interesting performance as Bond. Worse is the continued butchering of villain Blofeld; it's no wonder Mike Myers found him so easy to satirise, Diamonds just makes what started out as a shadowy figure and unhinged megalomaniac into a cross-dressing pompous nit, Charles Gray getting the short end and putting the final nail into a character who was so strangely cut & pasted he never reached his potential. The rest are just bland scientists, goons & support - Jimmy Dean deserved more as Howard Hughes pastiche Willard Whyte, though Jill St. John is a surprisingly effective femme fatale as cocky Tiffany Case, even if by the end she just withers into a blithering idiot for plot purposes sadly. Mention must also go out to Mr Wint & Mr Kidd, easily the best thing about Diamonds; an eccentric, possibly gay pair of weirdo henchmen who are very well underplayed in a piece that has about as much subtlety as a brick tied to a falling anvil, thanks to Guy Hamilton's limp direction, that creates little sense of scope or travelogue or inventiveness with what little, frequently boring, set pieces are on offer - the best being the moon buggy chase, a delightful idea that works when it never should have.
Ultimately however, Diamonds Are Forever is a strange and unsuccessful experiment. It's trying desperately to go in a different direction from the last movie, only thereby losing the depth, scope and beauty of said film. It trades far too heavily on Sean Connery's natural charisma when he's just frankly turning up rather than putting anything else in, while the narrative is so bizarre the pieces never manage to come together as a satisfying whole, nor are there enough memorable supporting characters to carry it all along. Without question, the Bond film I have least enjoyed and one very much for 007 enthusiasts only.