However, my confidence in him, which at one time had rather waned, was fully restored since his belief in Alfred Inglethorp's innocence had been so triumphantly vindicated. 
I have never onde doubted Poirot's investigative abilities. 
mnli hypothesis: I have never onde doubted Poirot's investigative abilities.  premise: However, my confidence in him, which at one time had rather waned, was fully restored since his belief in Alfred Inglethorp's innocence had been so triumphantly vindicated. 