In 1157 the cathedral chapter of Sées, composed of canons regular, elected Achard as their bishop, and the choice was duly confirmed by Pope Adrian IV.

But Henry II of England intervened and named his personal chaplain, Frogier, or Roger, to the office, thereby vetoing Achard's election.

But the French king, Louis VII, was by no means pleased to see such a shining light of the Parisian church pass over into Norman territory, as is evident from a letter he then addressed to the prior of St. Victor's.

He was a generous patron of the Premonstratensian La Lucerne Abbey, in the diocese of Avranches (the foundation stone of which he laid in 1164), in which his tomb and a fine, though damaged, contemporary effigy can still be seen.

He was buried with the simple inscription Hic jacet Achardus episcopus cujus caritate ditata est paupertas nostra.