I would not be a bit surprised to learn that the British sub was intentionallly chosen by the Russians to free the Russian crew. As bad as it looked for the British to save the Russians - it might have been too costly politically for Putin to have the Americans get the glory. I found it odd that it took so long for the US crews to get the Super Scorpio loaded and ready. If it were an American sub you can bet they would have been there in a hearbeat. I don't doubt there was some diplomatic wrangling going on over this.
Maybe conspiracy theory on my part but I would not put anything past Putin.