HM Revenue and Customs statistics relating to tobacco tax gap estimates https://www.gov.uk/government/statistics/tobacco-tax-gap-estimates
Illicit Tobacco Partnership https://www.illicit-tobacco.co.uk/
Taxation and Illicit trade http://ash.org.uk/category/information-and-resources/taxation-illicit-trade/
Guidance for trading standards https://www.illicit-tobacco.co.uk/problem/undermining-tobacco-control/guidance-trading-standards/