The internet's full of them...
"CIRCLE LINE (ANTI-CLOCKWISE): Minor delays are occurring due to lack of available trains."
OK, *how* do they manage to lose them? And what ratio of spares do they have? And why is it always the Circle?
ETA: Oh, no delays now... I presume they found more trains, possibly down the back of the sofa?
(Viccy's got Signal failure instead. *Don't* get me started on the "functional redundancy" rant)