When it sought parliamentary authorisation, it was denied the southern section, and obliged to use the Monmouthshire Railway between Pontypool and Newport.

It opened on 6 December 1853, and was part of an important chain of lines between south-east Wales and Birkenhead; mineral traffic in both directions was dominant.

c. ccciii) authorised it to build from a junction with the intended Newport and Pontypool Railway in the parish of Llanvrechva to Hereford.

In partnership with the Midland Railway the LNWR suggested generous terms to the NA&HR in completing and working their line.

Negotiations dragged on with opposition from some LNWR directors, but the NA&HR were offered 4% on their capital outlay, but only when the Worcester and Hereford Railway was opened.

A working agreement with the LNWR was agreed, to come into effect when the Worcester and Hereford Railway was opened: at this stage its authorising Bill was in Parliament.

[1] The mineral traffic potential was hugely dominant: two sets of carriages would be enough for the passenger service, but the LNWR estimated that 1,000 wagons would be required.

)[4] In 1853 the NA&HR sought Parliamentary approval for leasing its line to the LNWR, and for extensions of its network to Swansea and Brecon; at the time Parliament was against large scale amalgamations, and these measures were rejected.

[2][5] The permanent way consisted of a double track of Barlow rails throughout the main line, Coedygric Junction to the Barton station at Hereford.

Services reached Newport Mill Street station over the Monmouthshire Railway, which had opened in 1852; its line was single at first, but it was doubled in April 1854.

[5] The attraction of South Wales as a considerable centre of the metal-working industries was not diminished, and the directors considered it important to make a connection to the district.

Crumlin Viaduct was finished in May 1857 and was opened for traffic on 1 June 1857, together with a further three miles of single line to Tredegar Junction (now Pontllanfraith) on the Sirhowy Railway.

The Taff Vale Extension was immensely important strategically, giving access to South Wales Valley lines and their mineral resources, at twelve junctions in 20 miles.

Coal trains ran from Aberdare to London and Southampton as well as Liverpool; bunkering ocean-going ships at the latter ports was an important part of the business.

As well as having more favourable gradients, this route avoided the Crumlin Viaduct, which had a weight restriction preventing the use of the heaviest and most powerful locomotives over it.

This disagreement became serious and the NA&HR suspended the working arrangement with the LNWR from 1 October 1854, and brought in the railway contractor Thomas Brassey and Company.

At the end of March 1855 the LNWR summarily withdrew their rolling stock, and for some time the NA&HR was in considerable difficulty, losing business as a result.

[1][4] The breakaway from the LNWR led to difficult times for the NA&HR, and it formed an alliance with the Oxford, Worcester and Wolverhampton Railway.

The two companies pooled resources to complete a third line, the Worcester and Hereford Railway, then under construction but experiencing difficulties.

[6][5][9] The route from Birkenhead to South Wales became an important trunk line for minerals: MacDermot, drawing on a report of 1856, says that "a considerable Mineral Traffic, from the interchange of Red [iron] Ore from Birkenhead for the Iron Masters of South Wales with Steam Coals back from that district to the Mersey began.

In return the West Midland Railway had running powers over the S&HR from Hereford to Shelwick Junction, the point at which the Worcester line joined.

[6] The ironmaster Crawshay Bailey and his business partners were anxious to bring iron ore and other minerals from the Forest of Dean to ironworks at Nantyglo, Dowlais and Ebbw Vale, and the route formerly in use had involved a stiff climb against the load up the Western Valley line.

[10] The LNWR had running powers over the Newport, Abergavenny and Hereford Railway, and wished to obtain a convenient access to the ironworks of South Wales; this desire was reciprocated by the ironmasters, and at the same time colliery owners needed a suitable route for their output to travel north.

On 29 September 1862, the eastern section of the MT&AR was opened to a south-facing junction at Abergavenny, a short distance north of the NA&HR, now WMR, station.

As the primary purpose of the line was mineral traffic to and from the north-west of England and the West Midlands, it was obvious a northward curve was needed at Abergavenny, and this was provided on 22 June 1870.

The obvious inconvenience led to complaints, and a resolution was reached in which a connecting curve to the south was provided by the LNWR, enabling trains from Abergavenny to run direct to Barrs Court.

On 2 January 1893 the Brecon Curve was brought into use at Hereford, enabling those trains to get access to Barrs Court station from the north.