'Impressed?' Brunel did a circuit of the console, and returned to where the Doctor was standing. He folded his arms. 'Now the shock has worn off, I am composed. I will prepare to be impressed when you tell me how it [the TARDIS] works.'
'Oh, I don't know,' said the Doctor with a casual shrug. 'It just does.'
'You don't know?' roared Brunel.
'Well, you see, I didn't build it.' He frowned. 'At least, I don't think so.'
Brunel stared at him. ‘You mean to say you have no idea how it functions, or who constructed it?’
'I know how the tea machine works.'
Seven in his cozy habitat
Well, technically it’s Seven’s TARDIS :-P
(i bet Eight changed it’s interior afterwards)