Another phenomenal performance by Sagan, who made things look easier than ever here despite the late climbs and the damp conditions. He had little in the way of support over the final few hundred metres but didn't appear to need it. His third win from four stages is mirroring his dominance at last month's Tour of California. For full results, reaction and pics from this stage as we get it, click here.
Sagan may not have things all his own way at tomorrow's 193km stage five though. The six categorised climbs might take their toll on him and suit a large and prolonged breakaway, but we have written off Sagan's chances in these situations before and been made to look foolish.
So join us tomorrow for our live coverage of stage 5, where we shall see if Rui Costa can hold on to the yellow jersey still further.