At the 1922 general election, Wallhead gained Merthyr from the Liberals. As the politics of the South Wales coalfield radicalised, this turned into a safe Labour seat, which he was to hold until his death. He was one of only five ILP MPs to retain their seats in the 1931 general election, after Labour withdrew their support, and initially supported their disaffiliation from Labour. However, in September 1933 he resigned from the ILP and rejoined Labour. He died the following year.
His daughter Muriel Nichol was also a Labour politician, and served as MP for Bradford North from 1945 to 1950.
References
Michael Stenton and Stephen Lees, Who's Who of British MPs: Volume III, 1919-1945