Alternate timeline Edit
In an alternate timeline, Alice Obiefune crashed the pot with Dave on the Doctor's head knocking him out, afraid that he would be killed by a Nimon as John Jones was. With the time in the TARDIS going backwards in jumps, the Doctor prevented both the death of Jones and the demise of Dave.
Moreover, observing a slug crawling on Dave, the Doctor guessed that the time regression was caused by something crawling over the TARDIS. This helped him remove the Time Vortex leech and restore the normal time progression inside the TARDIS, preventing its explosion. (COMIC: Space in Dimension Relative and Time)