"But there is one bank that can never run out of money. And that is a central bank of a government that has its own sovereign currency, such as the Bank of England in the UK. The Bank of England can always pay. It can never fail. Because as the creator of all money, it can simply mark up its account with the government, and issue some more currency at will whenever it wants. The relationship between the Bank of England and the government is crucial here. The Bank can always lend what the government wants. So there need never be a shortage of money, most especially in situations of the type that now exist."
https://www.taxresearch.org.uk