In Tolkien's very earliest stories dating from 1917, now published as The Book of Lost Tales volumes one and two, framing device was a mariner called Eriol who found his way to Elfland, and heard the stories sung and recited in The Room of the Log Fire, in The Cottage of Lost Play.
This Eriol was therefore the link between the ancient legendary or mythic world - and the modern world; and over the next decades Eriol became variously re-named and transmuted through AElfwine in the early versions of The Silmarillion in the 1920s and 30s, through the Lost Road fragment of 1936 and the Arundel 'Arry' Lowtham character of the Notion Club Papers of 1945-6 - all of whom were mariners who reached Elfland (Tol Erresea) and brought the ancient legends back to Middle Earth (i.e. the British Isles).
But in the end, it was Bilbo Baggins who did this job - as described in the Prologue: concerning Hobbit to the The Lord of the Rings ^
So Eriol = Aelfwine = Arundel = Bilbo.
Cottage of Lost Play = Elrond's House in Rivendell
Room with the Log Fire = Hall of Fire