Do they actually talk about Theo? Pippa tells Boris how terrifying it is that Theo is so so fixated on her, and she loves him too but she knows that she could never love him with the all-consuming love that Theo wants, and Boris tells Pippa how he adores Theo but Theo just can't fully accept his love and sometimes that makes Boris frantic... and they have very carefully had this conversation somewhere where Theo ought never to have overheard any of it, but because Theo is a human disaster with the worst timing in the world, somehow he eavesdrops at least some of it. And fixates on 'They're TALKING ABOUT ME BEHIND MY BACK" instead of "Gosh, they both love me so so much."