MailOnline analysis of Britain's spiralling PIP bill names Labour-run constituencies of Liverpool Walton, Blaenau Gwent and Rhymney, and Merthyr Tydfil and Aberdare as the hotspots.
Dubbed the 'Welsh Tube', the ambitious project will stretch a staggering 105 miles (170km), linking the capital Cardiff with outlying towns including Merthyr Tydfil, Treherbert and Aberdare.
Jac Sexton, from Aberdare in South Wales, had only just started working as a barber when he suddenly began experiencing dizziness and slurred speech in October 2024.