Sorry, weak film! Don't recommend.
Compare this one to 1969's "The Italian Job." Much better story, action, characters, plot development, humor, and the dame was much better looking in TIJ.
I agree that Ustinov was good in this film, but everybody else was pretty lame and the "LSD-dreamlike" opening sequence is just hopelessly poorly done.
My god! If I was a jewel thief dealing with inept scum like Ustinov, I'd be watching for Turkish "watchers" which were always lurking about so obviously. This film lost it early on.
This must have been some kind of European-run flick. Pretty boring.