Paul Johnson of the Institute for Fiscal Studies (IFS) points out that such calculations should take account of the behavioural changes the tax causes: an IFS study claimed the new rate could diminish revenues, because it provides a disincentive to those close to the threshold to carry on earning and makes mobile high earners less likely to come to Britain.

ECONOMIST: A fresh political row over the taxation of high earners

Those bags and briefcases that cross the office threshold each morning likely carry employee-owned smart phones, tablets and laptops.

FORBES: The 5 Hot Tips to Secure Your BYOD Workplace