Cyg X-1 spectra for for: Left: Standard accretion disc (red), modeled with KERRBB, and a hot Comptonising plasma (blue) giving the high energy emission – as sketched in the top right corner; model (a). Middle: Standard accretion disc entirely covered by a warm Comptonising plasma (green), and then an inner hot Comptonising plasma (blue); model (b). Right: Same as middle panel, but with the spin fixed at a_BH = 0.1. Note: the low BH spin is fully consistent with the X-ray spectral data.