Howard R. Chesser (Charles Grodin) assesses diamonds for sale for a living, and makes a fair profit at it, though nowhere near as much as the Diamond Exchange at 11 Harrowhouse Street in London does, so couple that with the snobbish disdain the staff there hold him in, in particular the snooty but dangerous boss (John Gielgud), and it's not his favourite place to be. But what can he do? He's a self-described spectator in life, meaning he never thinks he's going to amount to much, though he is proud to have snagged rich girlfriend Maren Shirell (Candice Bergen) whose passion is zooming around in fast cars. But one day something happens to shake Howard up...
Nothing like a heist movie to do that, is there? Mind you, Howard pretty much stayed in the same frame of mind throughout, and if it were not for narration we would not be privy to his feelings at all, which was presumably why it was included. However, not every version of this movie carried the voiceover, which indicated the studio felt the proceedings needed an extra bit of business to sell it to the audience, and also in light of how drily humorous, verging on the sarcastic, Grodin's narration was we could surmise this was one of the least enthusiastic jobs in that area until Harrison Ford had his arm twisted to perform the same duty on Blade Runner.
Or maybe that's just what Charles Grodin was like, given he had adapted the popular Gerald A. Browne novel for the screen himself - Jeffrey Bloom penned the screenplay - with the character of Howard very close to his usual screen persona of the urbane but irritated by life modern male. Although there were quite a few Americans behind the camera, including director Aram Avakian making what surprisingly would be his final film at the helm, 11 Harrowhouse was a British production, which explained why most of the name cast were either ageing Brits from that thespian lineage, or character performers from that nation's deep well of such talent.
Oddly, there was an anti-establishment air to much of this, as if the Americans were keen to send up the United Kingdom's class system, and their British colleagues were only too happy to allow them to do so, but it was the central couple from across the Pond that would be the main force for striking back. Howard is puttering along, minding his own business, keeping his grievances to himself, when he is invited by millionaire Lord Bolding (Trevor Howard) to sell a large uncut diamond which he values at a high price; the diamond is then cut, he takes it back through Belgium to the nobleman's estate hidden in Maren's sports car, but whoops, along the way they are stopped.
And robbed, which puts Howard in a very difficult position since the gemstone was not insured, meaning he owes Lord Bolding a lot of money, but it so happens the old man has a solution to that: steal every diamond at the exchange. Easier said than done, especially given the opening sequence showed a previous robbery resulting in the criminals being blown up, no questions asked. But Howard is a clever chap, and devises a plan by roping in unappreciated Exchange worker James Mason to assist, along with a couple of cockroaches, one painted white, the other red. The vacuum cleaner-inspired heist itself is highly amusing, and the highlight, but for some reason the filmmakers decided they really needed something to top it for excitement, so the movie climaxes in a great big chunk of high speed car chasing, complete with very un-British exploding vehicles and admittedly very impressive stunts. Really it's Grodin's wry 'n' dry personality which sells this, one of the better (but not best) examples of this decade's love of a good heist. Music by Michael J. Lewis.