Peter, my condolences on your loss. Even if it's a pet, it's always a painful experience because these creatures manage to endear themselves to such a degree we forget they're not human beings.
Although they also make it difficult to think they're not.
Let's reformulate the situation and look at it this way: Harpo, then, was a great GUY. The kind you'd break bread with, down a couple of bottles of beer together, have an excellent conversation and a fun-packed weekend in the country. Your photos make a great memorial to him, so his life, despite the suffering, was not in vain.
Threads like this one send me off to check on Ben, my cat, and give him a bit of a scratch. I like to hear him purr...
Take care, Peter!