History is made as Trudy Harrison becomes Copeland's first Tory since 1930s

Electoral record books had to be rewritten after the Conservatives’ historic win in Copeland, which became only the fourth seat to be gained by a sitting government from the opposition in a by-election since the Second World War.

Copeland is such a safe Labour seat that the last time a Conservative was elected to represent the Cumbrian district was in 1931.

Trudy Harrison, who was born in 1976, is the first Tory in the former Whitehaven constituency since William Nunn, who was born in 1879 and ended his career as Britain’s last ambassador to Siam.

The Tories’ swing in Copeland of almost seven per cent from Labour was considerably bigger than the four per cent swing recorded by Labour when it retained the Hull North seat in a by-election in 1966.

Harold Wilson - who had a majority of just four seats after the 1964 general election - was so emboldened by that result that he called another general election, in which he increased his majority to 96, coincidentally the same majority that the Tories would have if they replicated the Copeland and Stoke Central results at a general election today.

The last time a sitting government gained a seat in a by-election was in 1982, when the Tories, in the final days of the Falklands War, took Mitcham and Morden from the former Labour MP Bruce Douglas-Mann, who had defected to the SDP. The net swing from Labour to the Conservatives was 10.2 per cent, with Labour coming a disastrous third.

Labour’s leader at the time of that result was Michael Foot.

The only other seats gained by an incumbent government since the war were the 1960 Brighouse and Spenborough by-election, won by the Conservative and National Liberal candidate Michael Shaw, and the 1953 Sunderland South by-election, won by the Conservatives during Sir Winston Churchill’s final term as Prime Minister. The 1966 Hull North result does not count as a “gain” as Labour already held it.

Another statistic that makes uncomfortable reading for Jeremy Corbyn is that Labour’s share of the vote has gone down in every by-election since the EU referendum, with the exception of the Batley and Spen by-election, which was not contested by the Conservatives or LibDems following the murder of the Labour MP Jo Cox.

In David Cameron’s former constituency of Witney, Labour’s vote dropped by more than two per cent; in Zac Goldsmith’s former seat of Richmond Park Labour lost more than 8 per cent of its share, and in Sleaford and North Hykeham it fell by seven per cent.

While Labour won Thursday’s Stoke-on-Trent Central by-election, its share of the vote fell by more than two per cent.