When the First Doctor, Vicki Pallister, and Steven Taylor first landed at the shore of 1066 Northumbria, they found a Viking helmet near the water. (TV: The Time Meddler [+]Loading...["The Time Meddler (TV story)"])
The same helmet appeared in the Remembered TARDIS when Vicki and Steven remembered these events. (TV: The Time Meddler [+]Loading...["The Time Meddler (TotT TV story)"])