A new two-part TV series about the construction of the Crossrail tunnels and their fit-out into an operational railway starts this week on BBC. With exclusive access, this returning series follows the construction workers of Crossrail as they battle to finish the final stages of the new Elizabeth line beneath the streets of London.

The cameras follow the engineers, technicians and train staff who are under pressure to complete their section of the project, including building and fitting out 10 brand new stations, learning to drive the new fleet of trains, and testing the 21-km twin tunnels beneath London, in a bid to make it safe for the public.

The first episode starts with a dramatic moment where they test their trains for the first time in the tunnels, with a comment that if this doesn’t work then the railway wont open.

Normally, over dramatic moments like this on TV documentaries lead to eye-rolling, as we all know what will happen. It’ll be fine. But thanks to the shock delay in opening the Elizabeth line, suddenly the drama is real.

Will the test train actually work as expected?

A test that was needed to run even as the tunnels were still not completed.

In light of the announcement of the delay, and the rows about who knew what and when, this is a documentary that’s going to be closely watched for hints of when the delays were first being spotted.

And there are plenty to pick from as the show highlights the difficulties faced by the construction teams to meet the ever closer deadline of the December launch, squeezing in test trains between engineering trains and worksites that shrink as more of them are converted into finished products.

It’s a very different sort of documentary from the previous series, as those were big machines digging big holes in the ground, whereas now were in the fit-out phase so it’s lots of details about turning concrete boxes into shiny new stations.

The first episode features the robotic trains that are fitting glass platform edge doors to Tottenham Court Road, and the team installing the huge ventilation fans inside Canary Wharf station.

Tracking the first eight months of 2018, the documentary also follows the people who will be driving the trains. A staggering 21,000 people applied, and just 310 got through, so we see their early stages of learning how to drive the new Elizabeth line trains and the sort of unforeseen things that can, but hopefully wont, happen on the tracks.

As a programme, it’s full of the grand build up that these shows usually provide, of dramatic moments as things don’t fit where they should followed by occasional relief when they get it right.

But it also doesn’t shy away from the elephant in the room – the shock delay that was announced in August 2018 — just as this episode finishes.

The first episode of Series 3 of The Fifteen Billion Pound Railway will be on Wednesday at 9pm, repeated on Sunday at 7pm.

Oh, and look out for the “hovercrafts”.

Photos from episode one of the series