@numericcitizen - what @rcrackley said. On BOTH counts. Not a photographer, but love to know how that colorisation thing is done - because when it works - WOW.
@JohnPhilpin Agreed it's wonderful! you asked to know how to do it, and the way I would do it using something like Affinity Photo is to create a black-and-white layer adjustment over the color image. Then select that adjustment layer in the layer palette, and use the eraser tool to erase the part of that black and white layer that you want to be colored. Or, instead of using the eraser tool, you could use a selection tool to select the part you want to remove and then cut or delete.