In April 1844 the Huddersfield & Manchester Railway & Canal scheme was proposed with the aim of building a line through Huddersfield with a capital of £600,000:
The use of a high-level line through Huddersfield — as opposed to the previous schemes which were for a low-level line running parallel to the River Colne along the valley bottom — gave better scope for connections through to neighbouring towns and cities. The scheme received the backing of those who had been opposed to the M&LR's low-level proposal.
The southern line would broadly follow the route of the existing Huddersfield Narrow Canal and the scheme included taking over ownership of the canal, along with the Huddersfield Broad Canal. As well as ensuring that the canal would not then compete financially with the new railway, having ownership of the narrow canal would also help simplify the task of building a new single-track railway tunnel to run parallel to the existing canal tunnel under Standedge.
The company's Parliamentary Act was given Royal Assent on 21 July 1845. A second shorter Act was passed in July 1846 to amend the route through Huddersfield and to formally agree that a section of the line — including the section through Huddersfield Railway Station — would be operated jointly with the Huddersfield & Sheffield Junction Railway (H&SJR). The two companies also agreed to jointly operate the new railway station.
At a meeting held on 28 February 1846, the company decided against becoming part of the proposed Manchester, Sheffield & Lincolnshire Railway (MS&LR). Instead, the MS&LR was formed on 1 January 1847 from the following companies:
In 1846, work began on constructing a new single track railway tunnel which ran parallel to the existing canal tunnel, with the canal used to move the excavated spoil. The contractor of the works was Thomas Nicholson (1784-1861), who had completed work on the SA&MR's Woodhead Tunnel the previous year.
In April 1847, experiments were carried out using a new form of guncotton (nitrocellulose) which had recently been discovered by German-Swiss chemist Christian Friedrich Schönbein. According to newspaper reports, the guncotton shots "exceeded anything the engineers or miners had before tested".
In August 1847, the half-yearly meeting of the company was told by engineer Mr. Mackworth that "the Stalybridge tunnel is completed for one-half its length".
On the morning of Saturday 9 October 1847, a miner was trapped by "an immense quantity of earth" falling in the tunnel. For the next 60 hours, his colleagues worked around the clock in shifts to remove the rubble. At the same time, equipped only with hammer and without food, the trapped miner managed to clear three yards of earth. On Monday evening, he was finally rescued.
Work was completed by March 1849 at a reported cost of £201,608.
According to a contemporary newspaper report, the tunnel was perfectly straight and "on a clear day a person standing at one end may see through to the other, and may even observe if a person crosses the mouth at the opposite end".
It is estimated that nine workers were killed during construction. The following were noted in contemporary newspaper reports and parish records:
A single-track line between Huddersfield and Heaton Lodge Junction (near Colne Bridge) was opened on 2 August 1847, following a favourable inspection by Captain Simmons, the government inspector of railways. The line was soon double-tracked.
Although the Huddersfield & Manchester Railway Company no longer existed as a separate entity, its logo was incorporated into the right-hand booking office of the railway station at Huddersfield.
The line was fully opened from Leeds, Dewsbury and Huddersfield through to Manchester on Friday 13 July 1849, with over 1,100 tickets issued on the day.
Much of the line was increased from two to four tracks, with the exception of the Tame Valley side where there was not enough room to lay more track. Instead, a new set of double tracks were laid along the other side of the valley and this was known as the Micklehurst Loop, which was completed by the end of 1885.
The pressure on the shared section of line between Heaton Lodge and Thornhill was eased by the building of the Heaton Lodge & Wortley Railway, also known as the Leeds New Line, which opened in 1900.
The route of the Huddersfield & Manchester line (including the 1894 Micklehurst Loop) from Stalybridge through to the two junctions with the Manchester & Leeds Railway (M&LR) near Cooper Bridge (Bradley Wood Junction and Heaton Lodge Junction) is shown below, along with the earlier M&LR line (shaded red) and the Huddersfield Narrow Canal (blue):