How to politely tell friend to shut up?

[FluffyChiffonCake]

I have a friend who has been talking about the same thing for at least 4 weeks. Doesn't matter what we're talking about, he'll find a way to shoehorn the subject into conversation. I don't want to be rude but I'm getting fed up!

@FluffyChiffonCake You could sing "summer nights" at him in that style of the pinks ladies "tell me more,tell me more, like does he have a car?" Obviously complete with a dance routine or at least jazz hands

Can you send him on shopping errands in return for listening to his stories? He could be quite useful.