Analysis of information sources in references of the Wikipedia article "Harriet Harman" in English language version.
When the party is in opposition and the party leader, for whatever reason, becomes permanently unavailable, the deputy leader shall automatically become party leader on a pro-tem basis.
Chair, Human Rights (Joint Committee) (29 Oct 2015 to 3 May 2017)"
"Chair, Human Rights (Joint Committee) (1 Nov 2017 to 6 Nov 2019)
When the party is in opposition and the party leader, for whatever reason, becomes permanently unavailable, the deputy leader shall automatically become party leader on a pro-tem basis.