In the late 70s and early 80s economic monetarism was espoused by Margaret Thatcher and Sir Keith Joseph  who wanted a radical alternative to the prevailing Keynesianism of previous governments. The theory seemed to be simple enough. The idea was that the money supply was a key parameter of our economy. Therefore, if we wanted to control inflation, and it did need to be controlled at the time, all Government needed to do was control the supply of money. Inflation would then fall and all would be well. Very quickly the Government and Treasury economists learned that they could not actually do that. It was difficult enough to define what money actually was let alone control the amount of it. Is it base money M0, which is just the amount of notes and coins in circulation? Or is it M1 which includes travellers’ cheques and demand deposits? Or, maybe M2 which includes savings deposits? Or M3 or M4? For anyone who cares to look it up they can find out what MZM means. There are lots of ways we can create money and lots of ways to try to define it. If I write out an IOU that is a form of money. As Minsky famously said, anyone can create money. It is getting it accepted which may be the problem.
But if we think about it, we can see that the money supply, no matter how we define it, does not tell us anything much at all. If the Bank of England were to, say, create £10 trillion of banknotes and keep them securely in their vaults they would have absolutely no effect at on the economy. But if they were stolen and scattered around the country by dropping them from a proverbial helicopter then they certainly would have an effect. They would be spent. So it is not so much the amount of money that exists that matters. It is the amount of money that is spent.