There is nothing unprecedented about losing a Chancellor. Plenty of other PMs have dispensed with them - Thatcher with Howe and Lawson most famously. And plenty before them. So why is getting rid of @sajidjavid different? A few reasons:
1) For all the chat about differences between no10 and no11 I cannot think of another Chancellor who was as pliant and unchallenging to a PM than SJ. Nigel Lawson he was not, let alone Gordon Brown. Really. Eliminating him looks like cruelty, or paranoia on the part of no10.
2) Timing is v awkward to say the least. Budget is in less than month. & this is no normal Budget. It's the Budget that will define a parliamentary term. Work on it is quite progressed. @RishiSunak has been involved so the disruption may not be enormous, but then again...
3) This isn't just abt the removal of a Chancellor. It's abt a No10 strategy to "take back control" of financial decision making. It's about killing or muffling the "Treasury view" that tends to recommend constraint rather than splurging. So it may have major fiscal implications
You get a sense of that when you look at the reaction in the government borrowing market today. Interest rates on UK 10 year govt debt shot up after it emerged SJ was leaving. That's investors betting that a chunk more government debt is about to be issued. 
At heart this is about an institutional battle between @OdysseanProject & the Whitehall power hierarchy, where HMT is primus inter pares. Today isn't the end of that war. Or the beginning of the end. These institutional power structures run v deep. In a sense they define the UK.
@OdysseanProject Cummings hardly the first person to attempt to take on the Treasury view. As this useful thread from @prospect_clark explains, this kind of thing goes back to Wilson, and indeed before. Most of them failed. Is Cummings more likely to succeed?
So if you assume @RishiSunak will allow No10 to splurge as much as they want, who now becomes the most important other player in the UK economy? Step forward Andrew Bailey. Newly appointed @bankofengland governor. Appointed by @sajidjavid. Yet to take up his post...
If @OdysseanProject succeeds in muffling the Treasury view, the next battle will be with the @bankofengland and its new governor who will be duty bound to raise interest rates if the govt splurges and drives up inflation. Might the next chapter be an assault on BoE independence?
@OdysseanProject @bankofengland The Treasury view, from the former head honcho of the Treasury:
