The constituency was formed in 1918. Until then Brecknockshire and Radnorshire had been separate seats.
With a total of fewer than 6,000 voters, Radnorshire had one of the
smallest electorates of any parliamentary constituency.
The largest settlement in the largest constituency in Wales and England is neither Brecon
nor Radnor but the former mining town of Ystradgynlais.
Until two other mining
towns - Brynmawr and Cefn Coed y Cymmer - were excluded from the seat by a 1970s
boundary revision, Brecon & Radnor was regarded as a safe Labour seat.
Tonight’s count is taking place in the Food Hall at the
Royal Welsh Showground in Llanelwedd, near Builth Wells. This is where the biggest agricultural event in Europe is held annually. This year’s event ended only a week ago when tables here would have been
groaning under the weight of Welsh food and drink.
Why does this by-election matter?
As well as determining who will represent the constituency in Westminster, there is a lot at stake given the government's wafer-thin majority in the House of Commons.
The Conservatives are defending a majority of just over 8,000 here. Should they lose the seat, it will cut their working majority in Parliament to just one.
Such an outcome could make it harder for Boris Johnson to deliver Brexit on 31 October and would leave the prime minister more susceptible to losing a possible motion of no confidence.
Live Reporting
By David Deans, Andy Roberts and Ruth Thomas
All times stated are UK
Background on Brecon & Radnorshire
The constituency was formed in 1918. Until then Brecknockshire and Radnorshire had been separate seats.
With a total of fewer than 6,000 voters, Radnorshire had one of the smallest electorates of any parliamentary constituency.
The largest settlement in the largest constituency in Wales and England is neither Brecon nor Radnor but the former mining town of Ystradgynlais.
Until two other mining towns - Brynmawr and Cefn Coed y Cymmer - were excluded from the seat by a 1970s boundary revision, Brecon & Radnor was regarded as a safe Labour seat.
Ready for the ballot boxes
Tonight’s count is taking place in the Food Hall at the Royal Welsh Showground in Llanelwedd, near Builth Wells. This is where the biggest agricultural event in Europe is held annually. This year’s event ended only a week ago when tables here would have been groaning under the weight of Welsh food and drink.
Why does this by-election matter?
As well as determining who will represent the constituency in Westminster, there is a lot at stake given the government's wafer-thin majority in the House of Commons.
The Conservatives are defending a majority of just over 8,000 here. Should they lose the seat, it will cut their working majority in Parliament to just one.
Such an outcome could make it harder for Boris Johnson to deliver Brexit on 31 October and would leave the prime minister more susceptible to losing a possible motion of no confidence.
Read more about why this by-election matters.
Good evening
Welcome to our coverage of the Brecon & Radnorshire by-election - the first electoral test for new PM Boris Johnson.
People in the constituency have been voting to elect a new MP after 10,000 people signed a petition to remove Conservative MP Chris Davies.
Local Tories chose him again to be their candidate, and he faces five other contenders:
Our reporters will bring you the latest from the count in Llanelwedd followed by the result when it is announced. Stay with us.