Barring any last-minute legal challenges, the tobacco category - or a sizeable chunk of it at least - will go dark from 6 April.

This will mark the single-biggest change to the £15.3bn market [Nielsen MAT to January 2012] since the ban on tobacco advertising came into force in 2004. Yet no-one has a clear idea of how the ban will impact sales.

That’s because no other country has introduced such a ban in phases. In the UK, uniquely, only stores above 3,000 sq ft have to implement the ban initially - for smaller stores, it does not come into force until 2015.

So for the next three years, the public is going to have to get used to the perverse scenario of stores that are legally allowed to display tobacco products being located right next to others that are not.