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X-ray reverberation shows that the corona is compact comma within 10 gravitational radii of the central black hole comma and irradiates a disc that extends down to or near the ISCO. However comma these results appear in tension with recent Swift disc reverberation results comma where the time delay between X-rays and UV-optical is much larger than expected from the standard reprocessing model in which a compact corona irradiates and thermalizes a thin accretion disc. In order to explain these disc reverberation results comma two suggestions have been madedoublePoint either openPar1closePar the thin disc is truncated with a hot inner flow or openPar2closePar absorption and scattering from the broad line region affect the time lag measurements. Neither of these two scenarios can be properly tested with Swift alone. XMM-Newton is required.