According to The Economist the “sin taxes” applicable to gambling, alcohol, tobacco and fuel are all producing fewer revenues.
In 2010-11 sin taxes produced 10% of all revenue.
It is little wonder that every New Year the most popular resolutions revolve around quitting drinking and smoking:

53p on a pint of beer,
£2.18p on a bottle of wine,
£8.54 on a bottle of whisky,
For cigarettes 75% of what you pay goes in tax.
Vices have been taxed to death and are consequently in decline.  The prevalence of smoking is down to about 22% of the population in 2010. Even drinking is in decline.
The betting duty returns are also in decline down from GB£ 536 million in 1999 to an estimated GB£339 million in 2011.
Unlike smokers and drinkers, the gambler has never had it so good. The payout to punters has never been higher. A compliment to the efficiency of the industry.