"Yes, Ariana might have made a desperate bid for freedom and killed Kendra in the struggle," said Auntie Muriel thoughtfully. "Shake your head all you like, Elphias! You were at Ariana's funeral, were you not?"
Harry Potter and the Deathly Hallows
I can find "shake your head". I think, in this context, it means:
- To express confusion or bewilderment about something that has just happened or been revealed. This usage does not always indicate a literal movement of the head.
But I don't really understand the whole phrase: "Shake your head all you like". What's it supposed to mean?