>Promo pic for McLaren P1 (see attached)
>
>The aircraft in the background has at least 4 turbofan engines, in twin-pod configuration. That configuration is not commonly used. There are some examples such as B-36 and B-47 but those use twin turbojet, not turbofan, engines.
>
>I'm 99% sure it's not a B-52H, you can Google images for those engines, the inlet looks significantly different.
>
>It's defeated my Google-fu so far ...

Actually, the B36 was piston driven.
http://freepages.family.rootsweb.ancestry.com/~pknox/b36/engine.html