The Butterley Company of Ripley, Derbyshire, was contracted by the Midland to manufacture and assemble the trainshed. This was undertaken even before the erection of the red brick walls and once complete, the cast iron mass stood for a short while on its own. Since the 4½ acres of station was suspended 20-foot above street level, the supporting columns and wrought-iron floor required strength testing before any laying of tracks could commence. This was conveniently tied in with the assembly of the trainshed by the aforementioned Butterly Company, when hundreds of tons of ironwork was laid on the elevated surface, pending assembly. Both the elevated flooring and trainshed stood robust, no significant structural movement being observed. The Midland could now claim to have the world’s largest single-span structure; it was indeed a marvel to behold.
Meanwhile, a separate project had been initiated to establish the Midland Railway’s headquarters at the station, housed within a building which was also to serve as a hotel. Although Barlow had no influence in the final design, the Midland ensured that no half measures would be taken, and a structure which would complement, if not augment, the single-span trainshed was sought. Rather than selecting a specific engineer from its own inventory, the company offered the architectural task out on tender to eleven potentials by means of a competition, agreed in a Board meeting on 3rd May 1865. Sir George Gilbert Scott (a title carried after being knighted in 1872) was approached by the Midland to enter the contest, but initially he declined. Scott’s first major Gothic-style work had been the Martyrs' Memorial in Oxford, designed by him in 1840 and completed three years later. Indeed, what could be considered his finest masterpiece was to materialise when he was finally convinced to enter the design race by one of the Midland’s directors, Joseph Lewis, whom was actually a friend of Scott. During the autumn of 1865, Scott worked on his hotel design, based again on his favoured Gothic styling, hinting at the best of medieval architecture. The architect was successful in his endeavours and in January 1866, the Midland board approved his outstanding design. It would be another two years until the foundations of the hotel were laid, this being a result of the financial restraints imposed on the company by a Bedford to London extension which was significantly over budget.
The first public passengers services ran over the then new extension and into Moorgate on 13th July 1868. When originally designing the route, it had been decided to connect with the Metropolitan Railway by means of a spur which branched off from the terminal approaches, just before these passed underneath the North London Line. A tunnel was bored under the site of the proposed terminus, through to the Metropolitan’s lines at Kings Cross. Finally, passenger services began running into the terminus, now named ‘’St Pancras’’ after the parish it was situated in, on 1st October 1868, but this complex could accurately be described as being a shell at this time. The trainshed roof was standing, all complete, but there were no side walls, nor a hotel to grace the Euston Road. The aforementioned financial position of the Midland caused the delay in hotel construction and indeed, modifications to Scott’s original drawings were made. This included the removal of the top floor set aside as the Midland Railway’s headquarters. The lack of available funds had made it a more desirable option to leave the company’s head office at Derby, which in hindsight, was perhaps a sensible option given that the Midland’s lines radiated out of there.
Hotel construction began in 1868, shortly before the trainshed opened to passengers. The design exceeded the original specification set out by the Midland, comprising 300 bedrooms over the original amount of 150. In addition to these, there were also 100 sitting rooms. Some 9000 tons of ironwork and sixty million red bricks were used to produce a hotel with a façade stretching 565-feet across the Euston Road, comprising seven storeys and fourteen different types of limestone and granite. The eastern end of the building was graced with a clock tower measuring 270-foot in height, somewhat similar to that of St Stephen’s Tower at the Palace of Westminster, which would have only been recently completed at the time (although this was quite a bit larger, being 318-feet high). The eastern part of the hotel was substantially complete by the end of 1872, the year in which the clock was delivered from John Walker of Cornhill for the tower. However, it was until 5th May of the following year that this part of the hotel opened, and even then, the west side of the complex was far from finished. Completion of this came in 1876, concurrent with the cab ramps at the front, and rooms were opened in the spring. Again, the west side of the enormous structure had echoes of the Palace of Westminster, coming with a 55-foot-wide tower decorated with spire turrets, arched windows, and like the clock tower, loomed over the Euston Road. To the unsuspecting passer-by, it could quite easily be mistaken as a Cathedral, rather than a railway hotel. £437,335 was spent frescoing the interior, which included fixtures, fittings, and furnishings – by today’s prices that equates to £27,457,340. Similar care was taken when decorating the station booking office, this demonstrating oak panelling, the customary arched windows, and limestone columns.