Question and Spoilers about Sarah

I think that's just supposed to be the first clue that Claire and him knew each other. Cause he worked on the lift in that cafe across the street so Claire probably would've met him there...I couldnT tell if Sarah was in on it though

[deleted]

Sarah was genuinely worried about her relationship with Robert, because he kept talking about someone named Claire. She probably overheard him talking on the phone with Billy about the scam. Later, Sarah arrived on her motorbike at Robert's shop and they had a blazing row, because she nearly blew the whole thing by telling Virgil that he couldn't be trusted. To save his relationship with her, he let her in on the scam. This is made clear when Virgil, "Claire", Robert and Sarah go to dinner.