Ed McKelvey, an economist at Goldman Sachs, points out that the historically flat personal saving rate (once realised capital gains are included) means that households are, in essence, treating such gains as a perfect substitute for disposable income.

ECONOMIST: Rainy-day blues

In this world where every object was thrown away at the slightest sign of breakage or aging, at the first dent or stain, and replaced with a new and perfect substitute, there was just one false note, one shadow: the moon.

NEWYORKER: The Daughters of the Moon

The comparatively less-crowded outer gardens and paths along the 1, 670m-long Grand Canal were once traversed on horseback, so a bicycle makes the perfect modern substitute for exploring the great outdoor expanse.

BBC: Easy breaks from Paris

This time of year, celeriac can be a perfect non-starch substitute for potatoes in a warming meal, and can be prepared in a similar way.

NPR: The Vegetable World's Ugly Duckling: Celeriac

Immediately, Calderwood sent on Owens and within three minutes the substitute had pinged a perfect ball onto the head of Kyle and the Scotland cap bulleted a header into the net.

BBC: Sport - Football - Aberdeen 1-2 Kilmarnock

But with seconds left of the four minutes of injury time, Luka Modric's shot was deflected on to an upright and substitute Lennon was in the perfect position to slot in the rebound and spark wild scenes of celebration from the Spurs contingent.

BBC: Arsenal 4-4 Tottenham