Leadership approval opinion polling for the next United Kingdom general election

At various dates in the run up to the next United Kingdom general election, various organisations have carried out opinion polling to gauge the opinions that voters hold towards political leaders. Results of these polls are displayed in this article. The polling companies listed are members of the British Polling Council (BPC) and abide by its disclosure rules.
The date range for these opinion polls is from the previous general election, held on 12 December 2019, to the present day.
Leadership approval ratings.
Boris Johnson.
The following polls asked about voters' opinions on Boris Johnson, leader of the Conservative Party and Prime Minister of the United Kingdom.
Keir Starmer.
The following polls asked about voters' opinions on Keir Starmer, the leader of the Labour Party and Leader of the Opposition since April 2020.
Ed Davey.
The following polls asked about voters' opinions on Ed Davey, the leader of the Liberal Democrats since 27 August 2020 and acting leader from 13 December 2019 to 27 August 2020.
Siân Berry & Jonathan Bartley.
The following polls asked about voters' opinions on Siân Berry & Jonathan Bartley, co-leaders of the Green Party since 4 September 2018.
Nicola Sturgeon.
The following polls asked about British voters' opinions on Nicola Sturgeon, the leader of the Scottish National Party and first minister of Scotland. These polls asked the opinions of "British voters", not specifically Scottish ones.
Approval ratings for former party leaders.
Nigel Farage.
The following polls asked about voters' opinions on Nigel Farage, the former leader of the Reform UK, formerly named Brexit Party.
Jeremy Corbyn.
The following polls asked about voters' opinions on Jeremy Corbyn, the former leader of the Labour Party.
Preferred Prime Minister polling.
Some opinion pollsters ask voters which party leader they would prefer as prime minister: Boris Johnson (Conservative Party) or Keir Starmer (Labour Party). The questions differ slightly from pollster to pollster:
Preferred Prime Minister and Chancellor Polling.
Some pollsters ask voters which potential Prime Minister/Chancellor of the Exchequer pairing they would prefer: Boris Johnson and Rishi Sunak for the Conservative Party, and Keir Starmer, Rachel Reeves ( and formerly Anneliese Dodds) for the Labour Party. Each pollster uses the following wording for this question:
Hypothetical polling.
Some pollsters conduct surveys to compare figures who are not both party leaders. These could include a comparison of leading politicians within the same party (to gauge support for future leadership contests), or compare the current leader of one party to an alternative leader of a second. The politicians listed below include: 
Topical polling.
Coronavirus handling.
The following polls have asked people which leader they think would better handle the COVID-19 pandemic.