Soap climax watched by 20m

Phil Mitchell confronts Lisa on EastEnders on Thursday

Almost 20 million viewers saw Lisa Shaw unmasked as Phil Mitchell's would-be assassin in BBC One soap EastEnders, according to unofficial audience figures.

The overnight ratings show an average of 17.9 million people saw the 40-minute long episode on Thursday.

But the ratings peaked almost halfway through at 19.8 million people - 74.5% of the viewing public - as Lisa, played by Lucy Benjamin, was confronted by ex-boyfriend Phil (Steve McFadden).

The National Grid also reported that the end of the episode created the third largest power surge on record.

A distraught Lisa Shaw played by actress Lucy Benjamin

Lucy Benjamin admitted on BBC One's Breakfast News it was difficult keeping the secret.

"I have to confess I did tell my mum. I wasn't meant to but I had to get it off my chest," she revealed.

The rest of the cast were kept in the dark so as to ensure the plot did not leak out.

Benjamin added: "I asked them last night after the episode was shown if they did know and apparently nobody knew for definite.

"I think they had their suspicions but nobody knew.

"They were very good to me. If they did have me as their number one suspect, no-one pressured me to tell the truth."

Only the penalty shoot-out between England and Germany in the 1990 World Cup semi-finals and the 1984 climax of the Thorn Birds drama in caused a bigger increase in electricity demand, the National Grid said.

Shaw was the odds on favourite at 8-11 in betting leading up to Thursday's broadcast.

Viewers who betted correctly will not get a pay out until a conviction for the shooting is made, something that could be affected by yet another plot twist.

After the revelation Shaw and Mitchell traded insults in a dramatic row with Shaw admitting that she enjoyed shooting the ruthless Mitchell.

But Shaw ended up telling Mitchell that she still loved him and wanted to get back with him.

Cliff-hanger

The EastEnders storyline has gripped viewers since the former Queen Victoria landlord was gunned down outside his Albert Square home five weeks ago.

In Tuesday's episode, viewers saw Phil, played by Steve McFadden, discharge himself from hospital to confront his would-be assassin.

Thursday's cliffhanger was eagerly awaited. A Tesco store in Neath Abbey even went as far as installing television sets in the aisles so that shopping EastEnders fans would not miss the moment.

Going down: Phil's shooting attracted 17 million viewers

Thousands of bets were placed by punters who thought they knew the attacker's identity.

The BBC News Online poll had put Dirty Dan as the clear favourite to have pulled the trigger, with 29% of the votes.

The five main suspects were Steve Owen (Martin Kemp), Dan Sullivan (Craig Fairbrass), Mark Fowler (Todd Carty), Lisa Shaw (Lucy Benjamin) and Ian Beale (Adam Woodyatt).

Owen, Fowler and Beale also featured heavily in Thursday's episode, fueling questions as to their involvement in the shooting.

All were exonerated, but the programme ended with Mitchell vowing to "get" Owen and Sullivan.

The BBC had negotiated a delayed kick-off for a European football match to enable Thursday's special 40-minute episode of EastEnders.

The start of the Uefa Cup semi-final between Liverpool and Barcelona from the Nou Camp stadium began at 2010BST.