An Arthropleura and hundreds of Carboniferous Arachnids came through the Anomaly into the London Underground, and the Arachnids set up a nest in the old bunkers by the Anomaly. After the Home Office became aware of the Anomaly incursion in the Underground, Nick Cutter, Abby Maitland and Stephen Hart investigated and found the Anomaly.
After delivering a message for Nick to Stephen, Helen Cutter apparently went through the Anomaly into the Carboniferous, where she waited for Nick. The Anomaly was secured by the Home Office and Special Forces, and the Carboniferous Arachnids were forced back through using torches.
After the incursion, the Anomaly site was secured by the Home Office and the Anomaly monitored by Connor Temple and several other Home Office scientists. Connor noted that the Anomaly's magnetic field was showing no signs that the Anomaly was weakening.
- In Episode 2.6 and 2.7, Oliver Leek had an Arthropleura in his creature army. It is generally believed by fans that Leek obtained it via the London Underground Anomaly in the new timeline.
- In most of the shots of the Anomaly, it was around two metres, but in the shots of Carboniferous Arachnids returning through the Anomaly, it was only about a metre tall.