Eric Hughes, a cryptology expert with Simple Access, an electronic-commerce consulting firm, conducted his own experiment: at a technical conference, he issued a roll of pennies to every participant and explained that there was a one-cent charge, payable into a box beside the door, each time anyone entered the main room.

ECONOMIST: So many ways to pay online

Previously under the self-assessment rules, you could avoid the penalty charge for a late filed tax return if all the tax payable had in fact been settled.

BBC: Get ready for tax return deadline on 31 October