I don't think there is a consensus. I'm normally a 46, sometimes a 48, and the Richard in a 46 was too fitted on me. More fitted than SS13 version in a 46.The 48 I haven't tried on yet, but it's apparently waaaay bigger than the 46. Measurements on Ssense seem to back that up.
Length was a tad too short for my liking. I would need to size up to correct that, but then it'd be big in the chest. Plus, didn't love the way it draped - mohair just kind of hangs there, would rather it be another material.