Well, I'm not going to argue with James' estimates but...
Total tax revenue from tobacco for the current financial year was £9.5 billion or £12.1 billion if you include VAT. Which is 2% of the total revenue.
A lot of money!
Now you can massage figures to say what you like, of course, but apparently the cost to the NHS of smoking is about £2.7 billion. But when you add in things like fires caused by smoking, cleaning up cigarette butts, apparent loss of productivity (yes, that old chestnut), absenteeism from work (yawn) etc. apparently it cranks it up to around £13 billion.
Now that could be a load of old toot, but if that argument works, then if everyone packed up smoking, the savings would pretty much equal the loss in revenue.
Let's hope so - because if that's true, there won't be any need for the government to tax e-cigs.
Of course, the problem is the interim period. As smokers convert to vaping, there will be a drop in revenue but not a correspondingly noticeable saving. I think that's where the danger area lies...
Cheers
Adam