The Gasworks Tunnel, located just north of King’s Cross Station in London, consists of three parallel tunnels that carry the six tracks beneath Regent’s Canal. Each tunnel is 528 yards (483m) long and is equipped with two tracks, allowing trains to travel in both directions. The tunnels were constructed in stages, with the original opening in 1852, followed by additional tunnels in 1878 and 1892. In 1977, during a significant modernisation project, the eastern tunnel was taken out of use, and the remaining two tunnels were modified for bi-directional train operations.
To enhance capacity and meet growing demand, the eastern tunnel was reinstated as part of a major upgrade to King’s Cross and the East Coast Main Line.
Client: Amey
Sector: Engineering
Project Type: Fibre Optic Network
Requirements: Secure, high-speed fibre optic connectivity throughout the tunnel for operational communications and connectivity.
King’s Cross Station — one of London’s busiest transport hubs — has long been constrained by a track bottleneck, with 12 tracks reducing to 4 in a 100m section. A major redevelopment project at King’s Cross Station included the refurbishment of a historic tunnel system to support modern infrastructure.
As part of the re-development Network Rail planned to re-instate the third eastern bore, a gasworks tunnel that sat dormant alongside the western and central operational tunnels, thus increasing track capacity by 50%, renewing life-expired track, adding higher speed turnouts, new drainage, and improving journey times.
While the western and central bores are active, the eastern bore — unused since the 1950s — had become a dumping ground for thousands of tonnes of spoil.
ACCL were commissioned to design and install a fibre optic communications backbone to connect precision monitoring instruments and deliver real-time structural movement data to engineers inside the redundant tunnel so excavation and re-development could take place with access to structural integrity and robust communications and connectivity of all equipment and precision tools.
We conducted a comprehensive site survey and risk assessment to map the tunnel environment and specify optimal pathways for fibre runs.
Installation of ruggedised fibre optic cable to withstand environmental pressures such as moisture, vibration, and physical wear, routed to a secure cabinet at each of the five wall-mounted total stations.
Precision termination and testing to guarantee bandwidth and signal integrity over long distances.
Coordination with tunnel engineers and site managers to integrate with existing services and schedule works during low-activity windows.
ACCL’s rapid, precise, and robust comms installation enabled Network Rail and its contractors to execute one of King’s Cross’ most significant capacity upgrades in over half a century — with confidence in structural integrity, enhanced safety, and zero operational disruption.
Construction within the tunnel went as planned with no closures. The monitoring systems and communications system has stood the test of time and provided accurate reliable communications and data
Construction was able to proceed with assurance of tunnel integrity, as part of this major redevelopment.