Hello
Another possible candidate...
General Sir Francis Seymour
https://en.m.wikipedia.org/wiki/Sir_Francis_Seymour,_1st_BaronetHas GCB (breast star)
Has Order of Medjidie (neck decoration)
Served in Crimea (second medal)
Has Legion d'Honneur (third medal?)
Can't see a Belgian decoration, if that is what the sash is, but Wikipedia suggests he was known to King Leopold I, so a possibility.
The thing that makes me think that this
isn't Sir Francis is that he also had the Grand Cross of the Order of Saxe~Ernestine, which is very different from any worn by the subject in the portrait, but perhaps this was not authorised for wear in uniform?
Still just a guess though!
Best wishes
Brian