Someone posted a question on a thread I saw a while back, which is, do Primarchs eat? As in, do we ever see them eat in the novels? The answer is yes!
Of course, one of them is Leman Russ. Eating and drinking copiously, as expected. This is a great scene in general - his first meeting with Horus, in Wolfsbane.
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(Horus is definitely not jealous.)
Also this happened: