"...I thought the reason the Saudi's were doing it was to screw up investment in western shale oil which would wipe out a lot of their customers..."
Not at all old lad. The House of Saud (with a little prompting from that nice Mr Obama) has its prime intention as severely harming Iran - their implacable anemy/arch-rival - whose export of oil is the only thing keeping the Tehrani economy anything like afloat. Depress the price of oil, and the general populace in Iran become somewhat disenchanted with the Ayatollahs...
Mr Obama is pefectly happy to see Tehran deep in the mire, and with the added bonus of buggering up Boris, he has had a pefectly happy Christmas - with it all effectively done through proxies.
The EU's rush (under US prompting) for expansion eastwards has fuelled Boris's natural age-old paranoia regarding being encircled by the enemy. with the enemy at the gates. The EU foray towards the Ukraine was a step too far from Boris's point of view.
Also, in reply to Arnaut the less, who states "With the possible exception of Angela Merkel, please let me have the name of a single leader of a major first world country who is not a putz.", the delightful Frau Merkel might not be a putz, but she is a dyed-in-the-wool authoritarian not-so-ex Osti apparatchik who views German hegemony over an enlarged European Union as the Fourth Reich.