"Went for a 4 miler and then when I got back from work we took the kids swimming. Nice and knackered now." blog post at SoreLimbs.co.uk, January 18, 2011
About the word:
The slang knacker means "to kill or tire."
Etymologists can't be sure if there's a link between the adjective knackered and the knacker that means "horse-slaughterer."