Dead in Space was an opportunity to explore a theme that goes all the way back to the third ever Doctor Who story – a crisis on the TARDIS. I did it in Unfinished Business with CO, and in Theta Sigma with Tomb in Space. This one is a much darker, harder story than either of those, with The Doctor experiencing a real shock when he enters the dead TARDIS that fell through the time vortex and finds his own body and that of Susan in the burnt out console room.

What can he do to stop that future from happening? His first idea, to get Susan home to Earth and safety, doesn’t work. His second idea, blows the Laws of Time apart. Going back in time to interact with themselves before the trouble began is seriously naughty. And it was tricky working out the logistics of it. But I think it worked out in the end.

When this story first went online a few people criticised the idea of the TARDIS actually suffering a ‘hull breach’ after we have been shown time and again what it CAN withstand. But those criticisms were silenced by the scene at the end of Last of The Time Lords when a ship crashed through the walls. That, of course, was something a bit more surreal than an explosion from within the TARDIS, but it proves that nothing is invincible. The TARDIS CAN be damaged.

The song at the start, Lake of Fire is there purely because it’s MY favourite Nirvana track. I know I’m too old and too uncool generally to HAVE a favourite Nirvana track, but as it happens I do. And for preference I like the MTV unplugged version of it. It strikes me, though, that The Doctor is BOUND to know a place somewhere in the universe where sentient beings live in fire or lava.

Where do bad folks go when they die
They don't go to heaven where the angels fly
Go to a lake of fire and fry
see them again 'till the Fourth of July

I knew a lady who came from Duluth
Bitten by a dog with a rabid tooth
She went to her grave just a little too soon
Threw a late howl at the yellow moon

Where do bad folks go when they die
They don't go to heaven where the angels fly
Go to a lake of fire and fry
see them again 'till the Fourth of July

People cry and people moan
Look for a dry place to call their home
Try to find some place to rest their bones
While the angels and the devils try to make 'em their own

Where do bad folks go when they die
They don't go to heaven where the angels fly
Go to a lake of fire and fry
see them again 'till the Fourth of July

And so, when it’s all over, they get to go to the zoo.