[Of course being really careful isn't really enough, but it's the best they can do, and still better than letting renegades run amok. At least Time Agents were usually aware of the more important things that had to happen.
He grins at Chekov's assessment, rather pleased to find someone actually comparing his wrist strap favourably to the TARDIS, which is pretty rare.] Convenient, maybe - when it works - but nowhere near as comfortable!
[He shakes his head, smiling.] And don't ask me exactly how the physics work. I'm a pilot, not an engineer. I can fly the thing, but I don't understand how it works! Not that the time-travel function has worked in years, anyway, I'm afraid.
((OOC: My brain now hurts from looking up closed timelike curves! I get the principle, but I couldn't work out if they applied to DW time travel or not!))