[7] When the Liberals split over Home Rule for Ireland, they took the Unionist side, and at the 1886 election he stood as a Liberal Unionist in Edinburgh South, but lost to William Ewart Gladstone's ally and former minister, Hugh Childers, who had been defeated in his previous district the previous December.

[9] In 1903 he supported Joseph Chamberlain's policy of Imperial Preference,[15] a proposed system of reciprocally-levelled tariffs or free trade agreements between different Dominions and Colonies within the British Empire which had caused a division in Unionist ranks.

He was knighted in 1905,[16] in the King's Birthday Honours,[17] but lost his seat at the 1906 general election to the Liberal Granville Greenwood, who won by a large majority of 1,159 votes (21% of the total).

[9] Purvis continued as an active Liberal Unionist, and in December 1908 he was one of several speaker at a mass meeting on tariff reform held in Stamford.

[20] The Liberal majority in 1906 was "decisive", and Greenwood had the support of most of Peterborough's railway and engineering workers made up a large proportion of the electorate.