An estimated 12.6 million viewers saw Coronation Street character Tracy Barlow jailed for murder on the ITV soap, according to overnight ratings.
Tracy Barlow will now leave the show after this Sunday's episode
Two separate endings had been recorded to keep fans guessing.
The trial was the culmination of a long-running storyline in which Tracy, played by actress Kate Ford, killed her boyfriend Charlie with an ornament.
Ratings peaked at the start of Monday's second episode, when the guilty verdict and life sentence were delivered.
An average of 11.3 million people tuned in for the first programme, at 1930 GMT.
At the end of the episode, the National Grid saw an electricity surge of 1,600 megawatts - equivalent to 650,000 kettles being boiled at the same time.
PAST SOAP CLIFFHANGERS
30.1m: Den divorces Angie (EastEnders, 1986)
25.3m: Sharon admits sleeping with Phil (EastEnders, 1994)
21.5m: Kristin revealed to have shot JR (Dallas, 1980)
20m: Lisa revealed as Phil's would-be assassin (EastEnders, 2001)
16m: Aftermath of plane crash (Emmerdale, 2004)
15.2m: Alfie and Kat marry (EastEnders, 2003)
14.5m: Little Mo hits Trevor with iron (EastEnders, 2002)
14.3m: Den is killed off (EastEnders, 2005)
12.4m: Mike has fatal heart attack (Coronation Street, 2006)
11.6m: Fred dies after heart attack (Coronation Street, 2006)
Average ratings. Source: Barb
An average of 11.8 million then watched the second instalment of the night's double bill.
The final scenes involving Kate Ford, who joined the long-running show in 2002, will be broadcast on Sunday.
In the run-up to the hearing, fans had watched as Tracy confessed her guilt to her mother, before deciding not to tell the truth in the courtroom.
She falsely claimed to have been a victim of domestic abuse and had planned her attack on Charlie Stubbs - played by Bill Ward - after he cheated on her.
But a spokesman for the soap described it as "a moral show where cheats and murderers rarely prosper".
"There was no way Tracy could ever get away with this crime," he said.
Separate endings were recorded to reflect the two possible verdicts
Tracy cried out as she was taken to the cells, having been told she must serve at least 15 years behind bars, claiming the killing was necessary to protect her daughter.
The character will now bow out of the show after Sunday's episode, in which she is seen sitting alone in her cell, contemplating her future.
And Tracy's young daughter Amy will leave the Barlow household to begin life with her father Steve McDonald.