'Never did trust satnav,' sniffed the Doctor.

‘You can't navigate your way through deep space without a proper guidance system.'

'I've got a proper guidance system,' the Doctor retorted. He tapped his forehead. ‘Up here. Trust me, I never get lost. Well, hardly ever. Well, not often. All right, sometimes, perhaps … but more often than not I …' He started to tap his pockets. 'Where did I put my glasses? I've left them somewhere…’