 Although entire UK railway network was nationalised in 1948 when they passed to the British Transport Commission, many bus services remained in private hands.The Western Welsh Omnibus company had used a unique system for identifying the depôt to which a 'bus was allocated and up to 1948, these comprised symbols of squares, triangles, diamonds and circles coloured in black or red with thin white edging for the blacks and thick black edging for the reds.Following that year these were all changed to diamonds with their longer length vertical and the narrow width, horizontal and other colours were introduced and each diamond carried thick black edging with a thin white 'tracer' separating the outer and inner diamond colours within the symbol.