Renly reveals Littlefinger's lie in AGOT

[Kienn]

That is only true because the OP did not put the passage they quoted in context. Jaime has just jousted against the Hound and lost. In that context, Renly (who bet on the Hound) saying that if Tyrion had been there, he would have won twice as much quite clearly means that he assumes Tyrion would have bet on Jaime also. And that, in turn, implies that Tyrion must frequently bet on his brother.

Again, in hindsight you can say this is obvious.

If all you know is that Tyrion is a gambler, then it's just a statement saying "if I'd had this other guy to bet against too, I would have won even more!"

At best you might say Renly would know Tyrion would bet on Jaime when against the Hound, it doesn't necessarily immediately translate to always betting on Jaime no matter what.

[Mad Monkey]

True, it's not a smoking gun by any means, but it's definitely a clue that someone with comprehensive awareness of the books (or a healthy suspicion of Littlefinger's statements) could have used to probe further. I don't blame Eddard Stark one bit for not catching this one detail; I do kind of look down on him for trusting the one man in KL who explicitly told him not to trust him, but that's about it. (Though I really wish he had listened to Renly even once about anything...) But this one detail is one of those things that, once everything shakes out and the mystery is solved, you can point as a clue; it's not really something that I can really blame someone who was living the story as it was happening to catch. (After all, I didn't catch it even though I read every chapter and knew that Tyrion probably had nothing to do with the knife or with the attack on Bran).

[Guest]

Wow, I never caught that either, Good Job OP! Poor Ned, if he'd noticed he might have realized what was happening.

[rystine]

I'm having trouble quoting posts for some reason, but actually, the chapter in which Tyrion reveals he would never bet against his brother is the one that immediately follows the Ned chapter I reference. And mrunderhill correctly points out how Ned should be aware of the dagger's story, given that Cat tells him everything. Good quote pull there.

Actually that exact quote was the one I was referencing in my earlier post when I said its not clear what exactly Ned was told. I should have quoted it earlier and explained myself better.

One important thing to remember about that quote is that it is from Ned's perspective. So when it is said that "she (Catelyn) told it all" we don't actually know to what extent she really did tell all. Did she explain every detail of every event and piece of information? Or did she simply "tell all" the important points? Either one would qualify as "telling all".

Also, the only thing that is really relevant to the situation regarding LF and the dagger is that LF claimed to know that it was Tyrion's. So how much of what LF told Catelyn, would Catelyn deem necessary to tell Ned?

When Catelyn told Ned about LF's involvement, did she explicitly tell him everything LF told her about how Tyrion won the dagger from him specifically by betting against Jaime? Possibly, although exactly how Tyrion supposedly won the dagger from LF is an irrelevant piece of information.

Did she tell him that Tyrion won the dagger from LF on a bet and leave it at that? Again, possible since it gets all the relevant information to Ned about how LF knew the dagger and knew who owned it, while also avoiding as many extra details.

Or did she just tell him that LF knew the dagger was Tyrion's? Also possible, since knowing how Tyrion came to own the dagger isn't strictly relevant, only that Ned thought it was Tyrion's.

TL/DR: Basically that particular quote doesn't necessarily mean that Ned was told LF's lie about how Tyrion came to own the dagger. It's certainly a distinct possibility that he was. But based on that quote (and that whole chapter actually) I'm not convinced of it.

Perhaps there are some passages in later Eddard chapters that shed more light on this, as I just reread that one chapter last night when I saw this thread pop up.

[Burdette]

Nice catch OP. Never noticed that before.

[ed Lannister]

good catch....... re-read these ASOIAF books over time and still more intricate details of plots and intrigues crop up.

[Maxpey]

It's always bugged me that LF made such a blatant mistake with the lie about the dagger. Why not say Tyrion made a bet on one of the many encounters which Jaime won? I know he had to think quickly, but still, for a master plotter that was quite a blunder.

Well, nobody's perfect, and as you said, LF had to think quickly because he was taken by surprise when Cat produced the dagger. Ironically enough, his clumsy lie could not have worked out better for his plan.

[Roadside Rose]

Nice catch!