A copy of this episode was discovered in 2013, restored and released to iTunes late in 2013. A DVD is due to be released in the UK in February 2014. As of 2021, a second DVD release included an animated recreation of the missing 3rd episode instead of the telesnap reconstruction as on the original release.
This episode takes place in the London Underground in 1975.
This episode was watched by 8 million viewers on its original transmission.