How well is the Tower of Joy showdown known throughout Westeros?

[I am a bastard's bastard]

i would think barristan would know/at least done some serious questioning after since ashara was vaguely involved and three of his buddies died. he never really thinks about it but from the few snippets he lets out he definitely knows more of the rhaegar scenario than he is letting on to dany

[Lonin]

Nothing is known amongst most of the population of Westeros.

It's somewhat surprising that Barristan Selmy, in his roll as LC of Kingsguard, was not more interested - to accurately update The White Book.

It's also strange that Cersei never lookled for some unfavorable (to Robert) information on Lyanna,

[LordManderlyAsDragonRider]

Is the fact that Lyanna and Rhaegar were an item of some sort known? I don't remember anyone ever mentioning it? You would think it would get "used" against the Starks somehow, Joffrey telling Sansa she is as slutty as her aunt or when someone mentions then Stark honour, expect Lyanna who ran away and started a war. Also if people think Lyanna was kidnapped, would it really never get mentioned?

[corbon]

It must be generally known that there was some sort of final showdown between the last few members of the still loyal kingsguard and ned's group,

Must be?

Why?

How?

I think that a bare-bones version of the story is common knowledge. Robert certainly would not want anybody to think that Hightower, Whent, and Dayne were alive and leading a resistance movement. The fact that Lyanna is dead seems to be common knowledge. Cersei knew that Ned killed Dayne. So did Cat. In fact, Ned killing Dayne seems to be well known at Winterfell. Something had to be said to the Hightowers and the Whents as well (especially the Whents, since Catelyn is a relative.)

No songs, though. Ned didn't provide enough detail.

What people know is that Ned returned Dawn to the Daynes and took Lyanna's bones home to be buried.

That leads to the inference that Ned killed Dayne, which Cersei 'knows' as do the Winterfell guardsmen. But the truth is that even we do not know that Ned killed Dayne, only that Dayne would have killed Ned if it were not for HR. Perhaps HR killed Dayne, perhaps one of Ned's other companions did, but not before Dayne had a killing stroke at Ned, which HR blocked, and then Whent or Hightower killed Dayne's killer. Or perhaps Ned killed Dayne. We just don't know, and neither does anyone else except HR and maybe Wylla.

It isn't necessary to tell the Whent's or Hightowers anything either. Their relatives simply disappeared in the war, these things happen. It might be nice to tell them something, but unlike returning Dawn its not important enough to justify the risk it creates (said risk being increased by returning Dawn in the first place).

Similarly it isn't necessary for Robert to know anything about them. Robert is the type to worry about them raising rebellion. The Targs are destroyed except for kiddie Viserys on Dragonstone, which is being handled, and thats all that matters to Robert. He's happy to pardon or ignore every other loyalist except the dragonspawn, if they bend the knee.

I think I remember someone telling me Jaime knew how Dayne had died, and he had textual proof. Many people knew about that.

He doesn't. The show put some stuff in the White Book, which show-Barristan would have filled out and show-Jaime read, but thats not in the books at all. Its a particuarly foolish error on the part of the show people. There is no way Barristan would have known without Ned having told him and Ned telling people about the ToJ showdown would create too much suspicion on Jon's background, suspicion which is notably absent in both show and books.

Well, it's a well-known fact around the lords of westeros.

Ser Gerold Hightower (a.k.a. The White Bull), Ser Arthur Dayne (a.k.a. The Sword of the Morning), Ser Oswell Whent, Lord Howland Reed and Lord Eddard Stark... Three KG from renowned and powerful families, the Lord guardian of the Neck and the Warden of the North were part of the battle. Obviously people would know.

Obviously people would know....

how?

i would think barristan would know/at least done some serious questioning after since ashara was vaguely involved and three of his buddies died. he never really thinks about it but from the few snippets he lets out he definitely knows more of the rhaegar scenario than he is letting on to dany

Ashara was not in any way involved that anyone knows of.

We suspect she might have been because we know where ToJ is and that Arthur was there. And that someone, a Rhaegar loyalist, must have been providing support to this isolated, run down, abandoned old watchtower.

He knows more about Rhaegar than he has told Dany yet, but nothing suggests he knows about ToJ at all - it happened after Rhaegar's death and during his own recuperation in KL after all..