Cucumber "tasty king"

I've just harvested my first "tasty king" cucumber and i have to say it's quite unpleasant tasting 

The packet clearly states that you should not remove the male flowers and that is supposed to be "bitter free" if you look it up on the web all the calalog's boast about it's bitter freeness not i wouldn't say it was very bitter per say but it is kinda unpleasant tasting, when you firest bite into it it seems ok but it leaves as really bad after taste that get's worse the more you eat.

Any idea's?

Was it because it was the first one do you think? or is there anything that could have caused it?