In 1860 the Manchester and Milford Railway received the Royal Assent to build a line from Pencader to Llanidloes, and the following year a branch to Aberystwyth was proposed; these lines were to join the Carmarthen and Cardigan Railway at Pencader. However the Manchester and Milford Railway was a narrow (standard) gauge line, so through-running at Pencader would not be possible. In fact, the M&MR was riven by indecision and lack of money, and it had to seek an amending Act for a time extension, which it achieved in 1865. By then Parliament considered the broad gauge to be a "general irritant" and the Carmarthen and Cardigan Railway was to be obliged to lay a third rail (to enable narrow gauge trains to run) between Pencader Junction and Carmarthen, and to grant running powers to the M&MR. Failing compliance the M&MR would be entitled to lay the additional rails itself. Seeing this as an unfriendly incursion, the C&CR applied for running powers over the M&MR to Aberystwyth, but this was turned down by Parliament.