It took me from 16 to 20 hours, done mostly at nights of the past few days. And believe it or not, but the lineart took two times as long as colouring.
There's a story behind this fanart, you know. Contains spoilers though, so don't read if you didn't see three first seasons of a new Doctor Who.
When Martha escaped from Master's ship, she did what Doctor asked her to: she brought back Rose from the other world, using Paradox machine of the Master. Thanks to Tardis changed into a Paradox machine, Rose once more became the Bad Wolf, this time with ability to control the power. Martha wasn't very glad to cooperate at the beginning, but later she learnt to trust Rose and vice versa.
Master, knowing that this duo is plotting against him, decided to kill them by himself. But girls were already waiting for him, ready. When Doctor was imprisoned, they decided to fight in their own way. And it meant one thing: no mercy.
I really suggest to download it, to see all these little details you won't be able to admire in a small size: the little Tardis key-chain and the "wanted dead or alive for the crimes against the master" poster on the wall. Notice that there's a card with number "10" sticked to the poster.
During the whole process of making I was listening almost only to "U+ur hand" by P!NK. It fits into the atmosphere nicely, so if you want listen to it: [link]
Doctor, Master, Rose, Martha, Lucy (c) "Doctor Who" series creator