If they're in close contact I imagine Lyall would be able to tell what happened (he's used to suddenly becoming human and he's quite good at identifying werewolves!). Being at the same café or waiting at a street corner or something like that. A log would be great!

Plus then Javert can explain to Lyall how to use some of his magic.

I'm basically clutching my face in glee at all of this happening to Javert it will be amazing.