If in the 1929 general election the Liberal vote had increased by 5%, the Conservative vote had decreased by the same amount and the Labour vote had remained the same, there would have been the following changes in seats:
Liberal gains from Conservative: 49
Liberal gains from Labour: 7
Total Liberal gains: 56.
Labour gains from Conservative: 17
Net Labour gain: 10.
Number of MPs elected:
Labour: 297
Conservative: 194
Liberal: 115
Others: 9
In Epping a further increase of 0.1% in the Liberal vote would mean that Winston Churchill would lose his seat. He won by a majority of 10.1% over the Liberal candidate.
Ramsay MacDonald would form a minority Labour government with Liberal support. With the Conservatives having their worst result since 1906, a Baldwin must go campaign results in his resignation as leader. He is replaced by Neville Chamberlain. But the new leader is less popular than Baldwin with non Conservative voters.
The Liberals make by-election gains from Labour in Shipley on 6 November 1930 and Islington East on 19 February 1931. In August 1931, negotiations for a national government of the three main parties break down because of Labour ministers hostility to Chamberlain. MacDonald forms a coalition with the Liberals. The Liberal Nationals and National Labour don't split from their parties.
The Labour/Liberal coalition stays in office until a general election in Autumn 1933 or Spring 1934. Voting is by the Alternative Vote as provided for by legislation enacted by the coalition. The Conservatives do well enough to secure a small majority of 10 to 15 seats. The Liberals do comparatively better than Labour, dropping to between 90 and 100 seats.
There is no general election in 1935 so the next one is not until October/November 1938, after the Munich agreement. In opposition to which a number of Conservative MPs, including Winston Churchill and Harold MacMillan, form a Progressive Conservative Party which allies with the Liberals. In the general election the Conservatives drop from first to third place, with thirty to forty Progressive Conservatives being elected. Labour win a small but workable majority.
In subequent years Labour and the Liberals are the two major parties. By the 1950s the Progressive Conservatives have joined the Liberals or returned to their parent party.