As Defence spending is set to rise it is obvious that the cost of the shopping basket must be increased.
Imagine if the budget was £100bn and MOD only needed £99bn and therefore planned a £1bn installation of swimming pools on the SSBNs, do you imagine the Treasury would cough up the funds?
Only by showing planned expenditure will exceed postulated budget can you get more money from the Treasury. The man is doing his job and having seen him, he looks the part.