On this page of our guide for Assassin's Creed Valhalla you will find the answer to the question how to get the ingot located in Evinghou Tower. This is one of the more problematic secrets in Oxenefordscire area.
The Evinghou Tower is located in the Oxenefordscire region - it is one of the vantage points / fast travel points. There are several different collectibles hidden in this place, with the only problematic secret being the ingot, classified as Wealth.
If you use Odin's Sight, you can determine that the ingot is stored on one of the higher levels of the tower. You cannot reach it from either the base or the roof of the tower.
Luckily, the solution is not very difficult - climb the tree adjacent to the tower in order to reach the shutter marked on the picture. It is boarded up, but you can destroy the boards at range using the bow.
You can already jump to the shutter. You have to deal with a single opponent who is in possession of a nickel ingot - the wealth.