In tunnelling, much of our work is hidden and frequently does not receive the recognition it deserves (and particularly not the recognition that we often think it deserves). One evening, leaving a site in North London which we were clearing after sinking a 15m ID shaft; driving a 100in (2.54m) shield 3.5km south and then a further 2.5km north; installing pipework to intersect the existing; and capping and backfilling over the shaft, I was stopped by a dog walker who pointed to the small control cabin on the surface and said: “Is that all you’ve built?”

Just once in my career have I achieved a completely different outcome, and this is a longer story:

Bank station for the DLR, 1980s

From 1989 to 1992, I worked on the hand tunnels section of the DLR Extension to Bank Station, working for Tony Edwards and Mathew Warren and with some extremely good gangs of hand miners who worked for Joseph Gallagher Ltd (JGL). With Josie and Andy Tasker on site for much of the time, this was an incredible learning opportunity for a young engineer. The work was executed to a very high standard, with beautiful timber work on display everywhere.

The passenger connection to the Northern Line required the encirclement of an existing passageway, which was to remain open throughout the works. Hence, we started by installing a protection canopy within the existing tunnel, to protect people passing through from the risk of loose tiles falling.

We then brought a cross-passage in from our adjacent concourse tunnel. This started as sidewall headings excavated and filled with concrete which went over a Northern Line running tunnel, exposing the segments as we progressed.

The central section then followed, building arches between the concrete sidewalls, followed by an in-situ concrete invert. We then broke out for a short section of SGI rings before going back into a timber heading, coming against and then driving over and encircling the existing tunnel. Building the first ring was probably the hardest survey and setting out task that I have had to work through.

We then turned 90-degrees right and carried our new encirclement a few metres before casting a headwall between new and old. Turning through 180-degrees, we continued the encirclement and brought in two further cross passages. Each junction required huge steel beams with virtually no installation room, and as this was before the days of 3D and 4D models, the usual installation method statement was the note to night shift: “Install beam xxxx.” Only once was this followed by a note for the next night shift, saying: “Take out beam xxxx, turn it around, and put it back in”.

As the encirclement progressed, we had been installing support frames under the invert segment of the existing rings and, in a series of night possessions, we first took down the existing rings before installing a slightly raised deck and hanging this from the new surrounding tunnel. After each possession, the cladding in the existing tunnel was reinstated. Observing the travelling public, the odd one or two would look around trying to work out where the noise was coming from, but the majority marched on unseeing.

We completed the new floor in the encirclement, blocked off the three cross-passages and then, during a weekend possession, we stripped out the protective cladding and tidied up the flooring. When the station re-opened on the Monday morning, there were typically three types of reaction among travellers:

  • Most people would halt briefly and visibly wonder “where had that come from?” Unfortunately, we could not tell whether the next thought was “that’s impressive” or “if they can dig tunnels that fast, why does it cost so much?”
  • A few would look up, realise they were in unfamiliar territory, and turn around, returning to the familiar.
  • But a sizeable minority just carried on, walking straight through without batting an eyelid as though nothing had happened. Thirty years on, I wonder whether they actually ever noticed.

Some people you can never impress.