It wasn't the most thrilling two hours of television.

The ITV referendum debate suffered from the same flaw as the channel's 2015 general election forum: Too many politicians.

This time there were six on stage, wrangled by Julie Etchingham. The gender balance was impressive (five women, one man, and a female moderator) but ensuring everyone got their say stifled substantive debate.

But if the format was lacking, it gave a platform to a new political star.

Amber Rudd is probably not a name most viewers will have been familiar with before Thursday night. She is a Conservative MP, the secretary of state for energy and climate change, and a campaigner for Britain to Remain in the EU.

And she knows her way around a political joust.

Nicola Sturgeon was trailed as the heavyweight on Team Remain but when it came to it, her contribution was marginal. The format didn't help and the expectation bar was probably too high -- though she did land a few blows on Boris Johnson.

No, it was Rudd who led the pro-EU charge, firm and factual, listing the benefits of membership and Scullying the more outlandish claims of the Leavers.

Crucially, she framed empirical arguments in emotional terms. "'Just don't know' just isn't good enough," she swiped at the splitters. "As a mother, I won't take that risk with my children's future." Too many who argue for Britain's place in the EU sound like statistical spitfires, all numbers and no feeling. Rudd showed that Remainers could get the blood flowing too.

And she did something else: She beat up Boris Johnson, her colleague, live on national television. Rudd recognised the former London Mayor as the Brexiteers' strongest asset and slugged him mercilessly. At times it was hard to believe these were two politicians who share a political party.

"The only number Boris is interested in is Number 10," she zinged, reminding the audience that, despite his schtick, Johnson is just another politician.

Pressing him on the claim branded on the Leave campaign battle bus that it costs the UK £350m a week to be a member of the EU, Rudd got snarky: "We're going to repaint that bus and put a leprechaun on one end, and a great big rainbow on one side and a pot of gold at the end."

She saved her most devastating Boris-bashing until the final minutes of the broadcast.

"As for Boris," she proclaimed coolly, an executioner reading a death warrant, "he's the life and soul of the party but he's not the man you want driving you home at the end of the evening."

Wait, did she just imply...

Yes, she did. Yes, it was crass. What did you expect? An evidence-based review of inward investment opportunities after Brexit? "They pull a knife, you pull a gun," Jimmy Malone taught. Amber Rudd pulled a shoulder-mounted rocket launcher.

As well as debunking his EU arguments, Rudd was making a half-implicit case against Johnson as a future Tory leader. He's only in it for himself. Women don't like him. He can't be trusted. "You wouldn't want Boris driving you home" could come to linger the way Ann Widdecombe's "something of the night" jibe attached itself to Michael Howard.

Whether her take-down of the Eurosceptics will shift the numbers is not yet clear. What is clear is that Amber Rudd has a promising future on the anti-Boris wing of the Tory Party, for such is the new dividing line in Conservative politics.

Last night, Gisela Stuart offered the strongest, most cogent prospectus I have yet heard for a Leave vote. Engaging her immigrant shield to deflect accusations of Little Englanderism, Stuart prosecuted Brexit largely unchallenged and cast the question as one of democracy. The UK had a record of leading the Continent on everything from workers' rights to women's rights, she essayed; why can't we be trusted to make our own decisions? Expect to see the Out camp deploy Stuart more in the next two weeks.

But the stand-out performer was Rudd. She had the facts on her side and the stomach to go low and go personal. As survivors of the Scottish referendum will tell you, the former is almost pointless without the latter. In Amber Rudd, the Remain campaign has found its star and those speculating on future Tory leaders have a new stock to invest in.

Comment by Stephen Daisley, STV's digital politics and comment editor. You can contact him at stephen.daisley@stv.tv.