Farrell just short for Saracens
Saracens endured their first defeat of the season after Toulouse fought back to edge a heavyweight Heineken Cup showdown at Wembley.
The Aviva Premiership pacesetters led 16-7 heading into the final quarter through Chris Wyles' ninth-minute try and the accurate kicking of Owen Farrell.
But they buckled as four-time European champions Toulouse launched a fightback founded on brute strength rather than guile with France number Louis Picamoles driving over.
With three minutes remaining Farrell attempted to snatch victory through an enormous penalty from inside his own half, only for the kick to fall just short.
Deep into injury time and following a rousing spell from his team-mates, the England fly-half lined-up a drop goal, but it failed to reach the posts.
Not only was it Saracens' first loss in seven matches, but in the final half hour they were overpowered in the way they have punished all opponents until meeting Toulouse.
The result puts the French club in the driving season of Pool Three, but with Connacht and Zebre, two of the competition's weakest teams, completing the group, both clubs have a good chance of progressing to the knockout stages.
The eagerly-anticipated clash between two of the competition's favourites failed to match expectations, even if the 61,428 crowd - a British record for the pool stage - were subjected to a tense climax.
Lighting up Saracens' evening was the endeavour of wing Chris Ashton who was lively throughout, regularly testing Toulouse's defence in search of the try that his performance deserved.
Answering the call from England backs coach Andy Farrell to use the occasion to secure selection for next month's QBE Internationals, the 26-year-old all but guaranteed his place on the right wing against Australia in November 2.
He was involved in Wyles' try as space opened up on the right, swapping passes with the outside centre to creating the gap for his team-mate to dart over.
There was a suspicion that Ashton's final pass was forward, but referee Nigel Owens was satisfied it had gone backwards.
Ashton appeared to have been hauled back illegally as he threatened to break through Toulouse's defence and then he dropped a difficult pass with the line beckoning.
Three successive missed penalties from Luke McAlister proved costly, but when David Strettle was sin-binned for tackling Yannick Nyanga without the ball the French club took their chance.
A line-out drive pierced the heart of Saracens' pack with giant prop Census Johnson providing the power and Tolofua touching down beneath a pile of bodies.
Scrum-half Jean-Marc Doussain took over the kicking duties and completed the conversion, but a brutal hit by lock Alistair Hargreaves on Nyanga put Saracens on to the front foot.
Farrell missed a penalty but went on to land two in rapid succession, the second coming after Ashton, running at full speed, had almost plotted a route through the white shirts.
Toulouse, trailing 13-7, lost McAlister to what appeared to be a shoulder problem and the second half opened with Saracens taking command.
Ashton continued to look lively, a low kick putting the visiting defence under pressure and when they collapsed a scrum Farrell kicked his third penalty.
The bulldozing Johnston helped put Toulouse on the front foot, but a promising attack ended when Farrell stole possession, winning a penalty in the process.
Saracens were spending an increasing amount of time defending and while they were protecting their whitewash brilliantly, pressure was mounting.
Doussain kicked a penalty and then disaster struck for the Aviva Premiership club when substitute Picamoles picked up from the back of a five-metre scrum and just managed to roll the ball on to the line.
The conversion was booted by Doussain and Saracens' brave late attempts to win through the boot of Farrell came up short.