Drugs
Now, according to this article, last year the deficit was £927 billion:
http://www.telegraph.co.uk/finance/economics/7901306/UK-deficit-fears-reappear-as-debts-hits-927bn.html
Since I can’t seem to find a more recent figure (and it’s gone up anyway), we’ll stick with that. Now, thanks to Wikipedia:
http://en.wikipedia.org/wiki/Illegal_drug_trade
We see that the UN estimates US$321.6 billion on GLOBAL drug trade. I can’t find any figures on UK in my 30 seconds of googling, so I’ll divide by 10 and use that, for $32.16 billion.
So the first thing we need to do is convert to GBP, at the current rates. Google says 20447328000, so approx £2.04 billion a year.
Now, we divide this by 52 for one week – 2044732800/52 = £39321784.61538462, so rounded, £39,321,784.61.
Now, if we assume standard VAT of 17.5% on this, 17.5% of 39321784.61 is £6881312.30, so £6.88 million.
Now we know what the government would get each week, we can work it out by dividing the total deficit by the weekly tax.
£2044732800 / £6881312.30 = 297.1428574750197. So in actuality, it would take 297 weeks and a day-ish to pay it. 5 and 3.4 years.
Assuming 10% of the worlds drugs are in the UK (theyre not, it’s more like 1%), and the deficit has stayed the same (it hasnt, it’s now in the trillions if I remember correctly).
We’re looking at more like 50 years.
EDIT: This is in response to someone claiming if we legalised and taxed drugs in the UK the deficit would be over withing a week. YEP, I’M THAT GUY