Deus Segué Machina

A segué which suggests that the topic of conversation being moved to, is related to the one being moved from, when in fact they are entirely unrelated.

Person A: Nice weather we're having today, is it not?
Person B: Yes, quite, and speaking of the weather; where's that £5 you owe me?

Here, "And speaking of the weather," is the Deus Segué Machina.