The Brits will wear a cut-away coat with black waistcoat and black tie at a funeral, if they follow tradition strictly. Often a dark lounge suit and a white shirt will be enough though.
Butler shows, how you can substitute both cut-away and lounge suit at a funeral for something in between: a black jacket. With greyish striped trousers and black waistcoat the black jacket is a semi-formal colourless daytime attire, which spread after WW1, when cut-aways left the scene.
Unlike the cut-away, which can take a buff waistcoat and a light-hearted tie, I don’t think that the black jacket dress is a good match for a wedding. It is always black, grey, and white, and that appears too serious for a happy event like a wedding. The black jacket is better suited for a funeral.
Jacket & trousers: Steven Hitchcock, London.
Photo: The Journal of Style