It certainly doesn't sound like a real Nightingale, but the observer who found Britain's second, last Friday at Wells in Norfolk, was I'm sure glad it was one of these, not 'just' a Nightingale.
Actually on a recent trip to Ethiopia, during very heavy, and wonderful, spring migration through the region, I was struck by how similar Thrush Nightingale Luscinia luscinia is in jizz at least to Rufous-tailed Robin. It certainly was in comparison to the large, rangey, long-winged, long-tailed Eastern Nightingales Luscinia (megarhynchos) golzii, which were more numerous on migration. You wouldn't have imagined them in the same genus.
Mike Turnbull