They nudged clear at the Harrods Depository at the start of the sweeping Surrey bend and, after passing under Hammersmith Bridge, the Light Blue lead was three-quarters of a length.
But Cambridge's push to establish clear water was thwarted by a clash of oars that disrupted their rhythm and Oxford made them pay.
Once the Thames turned back in Oxford's favour for the final bend, Cambridge's challenge had been snuffed out and the Dark Blues pulled well clear to claim their expected emphatic victory.
Smith said: "It was a really tough race, especially by half-way, and Cambridge came close to making it their day.
"The difference between the two crews was our power, aggression and stickability.
"All the way along I knew we had good strength and it would take a lot to break us, and that really showed."
