Marcus Smith inspired Harlequins to a 50-21 win over Northampton, while there were also English Premiership victories for Newcastle, Gloucester, Saracens, Wasps and Exeter.
It was one-way traffic in front of a 77,825 crowd at Twickenham, as Northampton suffered their 11th consecutive loss in all competitions.
The 18-year-old Smith had a hand in five of Harlequins’ seven tries, while kicking five conversions and slotting a penalty.
Quins scored four converted tries and a penalty to take a commanding 31-0 lead at the break.
Northampton scored three second-half tries, including one from scrumhalf Nic Groom, but Harlequins scored three more themselves to wrap up a convincing victory.
In other notable results on Saturday, the Newcastle Falcons ground out a 20-15 victory over London Irish, Gloucester sealed a 20-16 triumph against the Sale Sharks at Kingsholm Stadium and Saracens continued their recent revival with a 46-31 defeat of the Worcester Warriors.
On Friday, Juan de Jongh scored a try as Wasps beat Bath 31-26 at The Rec, while Sunday’s only game saw the Exeter Chiefs extend their lead at the top of the Premiership to 10 points with a 30-6 bonus-point victory over Leicester at Sandy Park.
On Sunday, the Exeter Chiefs beat the Leicester Tigers 30-6 to move 10 points clear at the top of the Premiership.
Round 12 results:
Gloucester 20 Sale Sharks 16
Saracens 46 Worcester Warrior 31
London Irish 15 Newcastle Falcons 20
Harlequins 50 Northampton Saints 21
Photo: David Rogers/Getty Images