Why did you need a visa to get a cigarette? Canadians don't need a visa to enter the UK for tourism/transit/business, subject to some maximum amount of time (90 days IIRC, but definitely more than enough to buy a packet of cigarettes).
I was holding a carton of Marlboro Reds purchased in Berlin, so I didn't even need to buy any. I'm fairly certain we still need a visa, but it's basically an automatic process.
