I was just watching Top of the pops on BBC4 there and couldn't believe my eyes! Look at the band!

https://www.youtube.com/watch?v=T2hvkPyiAFE

Wonder if that was an image that stuck with Steven as we were at school together when John Lennon was murdered...or were the Janus created by the writer?

Janus was a 2 faced God in Roman mythology.

As with the aliens in this story he had the power to look into the future and the past.