20 Doctor Who Characters Who MUST Return

Martha Jones is the most underrated of modern Doctor Who companions, because she worked harder than almost all of them. Not only did she overthrow the Master's reign in Last of the Time Lords, she threatened to use the Osterhagen Key against Davros, and had to endure a few days working for Torchwood.

And does Martha get any credit? Wouldn't it be nice to see the Fifteenth Doctor apologise for not appreciating her more while she was travelling with him. Perhaps while they face down some extraterrestrial threat together?

The Mickey situation would have to be addressed, but there's no reason Martha can't easily return as a member of UNIT, or some other important military organisation. The War Between the Land and the Sea would be a prime opportunity.