A great early example of degeneration in Doctor Who. Whilst it's a little disappointing that we don't get to see much of the Second and Third Doctors during this plot, the first Doctor gets a lot of time to shine. It's also interesting that the TARDIS degenerates alongside the Doctor, as it is a concept that is rarely discussed when fans talk of degeneration.

In some ways, Timeslip feels more typical now than ever before. Although David Tennant's Doctor last year wasn't a degeneration per say, it's basically the same general idea of the Doctor returning to a past face, which has also been explored through the Curator's introduction in The Day Of The Doctor. Timeslip is a simple story, but in some ways it's also one that was ahead of its time.