With the government considering doubling prison sentences for those who pedal tax avoidance schemes, Crawford Temple says that it will not deter those criminals who are arrogant enough to think they will never get caught and enforcement is key: 

https://www.freelanceinformer.com/hmrc/would-hmrc-fine-itself-if-its-contractors-got-caught-up-in-an-umbrella-tax-avoidance-scheme/