Cardiff Blues survived a late Ospreys comeback to clinch a thrilling win in the Magners League.
Ben Blair scored 25 points, including two of his side's three tries, as the Blues ran riot in the first half following Nicky Robinson's opening score.
But Filo Tiatia and Wales lock Ian Evans both went over after the break as the Ospreys staged a dramatic comeback before running out of time.
The game was marred in the 81st minute when Blues and Wales flanker Martyn Williams was sent off for butting Ospreys replacement Jason Spice. However, that was not enough to prevent the Blues celebrating Christmas by frogleaping their opponents into fifth place in the Magners League.
The Blues showed a clinical edge as the Ospreys made a series of crucial mistakes during the first half, enabling them to cruise into a 27-6 lead. Robinson intercepted Justin Marshall's pass to race untouched under the posts in the seventh minute, then combined with older bother Jamie to send Blair over for his first try two minutes later.
Former All Black Blair put the Blues out of sight when he gathered Shane Williams's attempted chip to race 70 metres for a second on 22 minutes. Henson pulled back three penalties but a half-time talk from coach Lyn Jones galvanised a second-half recovery through Tiatia and Evans.
Yet the Blues held until they were reduced to 13 men in injury time when Mike Phillips (yellow card) and Williams (red) were dismissed.
Cardiff Blues: Tries - B Blair (2), N Robinson. Cons - B Blair (3). Pens - B Blair (3).
Ospreys: Tries - F Tiatia, I Evans. Con - G Henson. Pens - G Henson (4).
Referee: Tim Hayes (WRU).