Britain is eighth, comfortably ahead of comparable countries such as France and Germany, and not far behind world leaders such as Australia and New Zealand.

But the comparison with Yum Brands and Burger King serves as a good reminder to long-term investors that ROIC isn't a static number.

The atmosphere is much like the curio library of a Victorian gentleman scholar, full of elegant glass-and-wood vitrines, dimly ornate wall coverings, velvet curtains and engagingly stuffy wall-text.