On this measure, Italy drops from 12th to 21st place, while Germany falls from 5th to 9th position. According to PwC’s analysis, the UK’s “relatively larger projected working age share of the population” and flexible economy are the main factors behind its prediction that the country will be the fastest-growing economy in the G7 to 2050.

Its ability to forge trade ties with faster-growing emerging markets is also a “critical” component of this forecast.

Medium-term growth is forecast to average 1.9pc a year between now and then, compared with just 1pc in Italy and 0.9pc in Japan.

The UK Government has linked the state pension age to life expectancy, meaning by 2028 Britons will retire at 67, and at 69 by 2055, according to projections by the Office for Budget Responsibility (OBR).

Taking into account demographic trends, the share of people aged between 15 and 64 years-old is expected to fall to 55.2pc in the UK by 2100, down from 64.5pc in 2015, according to the United Nations.

This compares with 54.1pc by the end of the century in France, from 62.4pc today, and 52.5pc by 2100 in Germany, compared with 65.9pc today.

Japan is expected to see the share of its working age population decline to around 51.2pc in 2100, from 60.8pc in 2015. By the end of the century, 35pc of Japan’s population will be aged over 65 and 13pc aged over 85.