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There has been confusion around who can and cannot vote in the upcoming Caerphilly Senedd by-election – all due to recent parliamentary boundary changes.

The name of the local authority – Caerphilly County Borough Council – also hasn’t helped matters.

Here we break it down to explain the key differences so residents are no longer scratching their heads as to why they haven’t received a polling card.

The area known as Caerphilly County Borough – which has been in existence since Welsh councils were reorganised in 1996 has, for the most part, covered the areas of three constituencies.

Both Caerphilly and Islwyn have always been wholly contained within the county borough, while part of the Merthyr Tydfil and Rhymney constituency covered the north of it.

Up until the 2024 UK general election, these three constituencies were the same for the Senedd (and also for when it was known as the Welsh Assembly).

However, moves to reduce the number of Westminster MPs in Wales meant these changed last year.

Islwyn merged with Newport West to become Newport West and Islwyn, Rhymney split from Merthyr, joining Blaenau Gwent, to became Blaenau Gwent and Rhymney.

Some areas were also shifted around to ensure an even spread of population between the different seats.

Pengam (but not Cefn Fforest), Pontllanfraith, Maesycwmmer and Ynysddu all became part of the new Caerphilly constituency; while Bargoed and Gilfach were dropped and moved to Blaenau Gwent and Rhymney.  Aberbargoed, which was part of Islwyn, was also moved to this seat.

The confusion has come about because this by-election, following the death of Hefin David, is being held on the 2021 boundaries. This means residents in Maesycwmmer, for example, who voted in the 2024 UK general election cannot vote this time around.

Their Senedd Member is still Islwyn’s Rhianon Passmore – elected in the 2021 Senedd election.

Caerphilly County Borough Council has sought to clear up the matter by publishing a list of its wards and communities which will be able to take part in the by-election on Thursday October 23.

As reported previously by the Local Democracy Reporting Service, the council listed those borough wards as:

• Aber Valley
• Bargoed (not Aberbargoed)
• Bedwas and Trethomas
• Gilfach
• Hengoed
• Llanbradach
• Machen and Rudry
• Morgan Jones (Caerphilly)
• Nelson
• Penyrheol
• St Cattwg (Cascade, Gelligaer, Penpedairheol)
• St Martins (Caerphilly)
• Van (Lansbury Park, Mornington Meadows, Porset Park)
• Ystrad Mynach

More changes on the horizon

This by-election is expected to be the last time voters in Wales will go to the polls before sweeping changes to Senedd elections come into effect.

The whole of Wales will vote next May to elect 96 Senedd Members via a new ‘super constituency’ system.

These have been created by ‘pairing’ existing UK Parliament seat boundaries and distinguishing them by referring to their Welsh language names.

So, Blaenau Gwent Caerffili Rhymni will comprise the Westminster constituencies of Caerphilly and that of Blaenau Gwent and Rhymney.

Newport East, together with Newport West and Islwyn, become Casnewydd Islwyn.

These enlarged seat areas for the Senedd will each return six Senedd members under a new proportional representation system where voters choose a party, rather than an individual (unless of course an individual decides to stand as a non-party independent).

Caerphilly’s by-election candidates for October 23

• Welsh Liberal Democrats – Steve Aicheler
• Gwlad – Anthony Cook
• Wales Green Party – Gareth Hughes
• Welsh Conservatives – Gareth Potter
• Reform UK – Llŷr Powell
• UKIP – Roger Quilliam
• Richard Tunnicliffe – Labour
• Lindsay Whittle – Plaid Cymru