I.M. Foreman's One-Species Nongenetically Engineered Travelling Show was a complex space-time event. It was similar to, although not like, a TARDIS.
It was a space-time vessel but it had no extra-dimensional connections. It moved through space and time by retroactively building a site and disguising itself before/during/as it moved there. This process took years.
It was not designed for instantaneous (or even fast) travel, unlike a TARDIS. Unlike most TARDISes, the show could (and did) travel back into the Dark Time.
A by-product of this was that it sometimes knocked dents in space-time, luring other space-time travellers to the site. (PROSE: Interference - Book One, Interference - Book Two) It brought the First Doctor to 76 Totter's Lane ("Foreman's Yard"). (TV: An Unearthly Child) It brought Faction Paradox, the Remote and the TARDIS (with the Third Doctor and Sarah Jane Smith) to the planet Dust. (PROSE: Interference - Book One, Interference - Book Two)