The Cane is a Dead Giveaway

All they wanted to do was make Remus look English. The moustache, the neatly parted hair, and now the cane - David Niven anyone?

Remus: By Jove, old chap, what a ripping good idea!
Sirius (worried whisper): You take the cane away, Prongs, and Wormy holds him while I shave that... thing off.