Well, this isn't cool. Not cool at all.
Well, we do know he loves older women!
Even though the One Direction cutie pie was happy to watch his ex - and most def NOT current - girlfriend, Cara Delevingne, walk the runway, he certainly didn't have a one track mind! In fact, he not only managed to check out Cara's derriere, but he kept a good eye on Sienna as well!
Sienna even had him looking like a giddy school boy!
While we're sure they'd never cross any inappropriate boundaries, maybe they could double date because we bet they'd have a blast hitting the town together!
Ch-ch-check out more pics of the giggly twosome (below)!
[Image via GF/BauerGriffinOnline.]