[2] At a Westminster St George's constituency by-election in 1921, Erskine scored a notable victory standing as an "Independent Anti-Waste" candidate supported by an unofficial grouping of Conservatives, in a straight fight against the official "Coalition Unionist" candidate, Sir Herbert Jessel.

The Times newspaper gave much of the credit for the result to the support Erskine had received from its popular rival the Daily Mirror.

Using the campaign slogan "Economy without exception", Erskine attacked "the orgy of extravagance which has marked the last few years", extravagance not only by the government but also by the London County Council, while his opponent, Jessel, attempted to portray himself as the true anti-waste candidate.

[5][6] Speaking after the declaration of the result, Erskine said: I won because the whole country demands economy.

[2] Erskine retired from parliament in 1929 and was knighted the same year, in the Dissolution Honours of Stanley Baldwin gazetted on 28 June 1929.