Regarding Sunak's promise/pledge to increase defence spending, I would offer the following observations.
Firstly, as others have already said, he won't be Prime Minister from about September 2024 onward, so he won't have to deliver on anything he says.
Secondly, the articles with more detail seem to talk about the extra expenditure being on MUNITIONS. There is talk of more missiles, shells, bombs, etc.
I've seen nothing about increasing the size of the Army, buying more aircraft, building more ships.
While welcome/necessary, the purchase of more munitions will do little more than replace stock given to Ukraine, and increase our arsenal size to the point where we can fight a full blown war for more than 3 weeks.