Not only did the politician pretend to retire in order to halve his tax bill, the author claimed, he persuaded the Revenue's young chairman to help him figure out a way to save his earnings for himself.

Speaking at the Oxford Literary Festival, Lough said the antics of modern politicians and their families paled in comparison to the financial manoeuvring of Churchill, as he warns politicians must not be subject to such scrutiny they become "cardboard cutouts".

The details of Churchill's finances are examined in Lough's book No More Champagne, which is based on National Archives documents declassified in 2004.

They reveal the enormous debts the politician found himself in, including wine, gambling and a Harrods account built up by his wife, as well as the "two thick files" built up by the Inland Revenue dedicated to the Churchill finances.