It has been suggested that this tradition arose as the best of several circumstances: Friday pay-packets would lead to more drunken voters on Fridays and weekends; having the election as far after a Sunday as possible would reduce the influence of Sunday sermons; many towns held markets on Thursdays, thus the local population would be travelling to town that day anyway.
[2] The Levellers proposed that elections be held on the first Thursday in every second March in the Agreement of the People in 1647.
To call an early election, either a vote of no confidence in the government, which required a simple majority, or a vote in favour of an earlier election, which required a two-thirds majority of the House of Commons was needed.
This was held on a Wednesday as the returning officer wished to avoid a clash with the opening game of the 1978 FIFA World Cup.
Today, council by-elections are still occasionally held on days other than Thursday.