its not as if iv walked into an open man hole
I suggest that if you are going to go ahead with a claim that you get everything right, afterall you titled this topic
fell down a manhole at showroom when you now say you didn't fall down a manhole but actually slipped on a manhole cover. I'll accept for whatever reasons that the cover wasn't secure enough.
Secondly, there's a reason why insurance premiums are going up each year way above the rate of inflation and it's not to do with profit margins. Right or wrong it's to do with insurance under writers trying to catch up financially with all the extra claims that they've had to pay out on. This is turn means 'some' decide it's fair game to make a claim for whatever reason just to get some payback on their premiums. Guess what happens next? yes the premiums go up again and again and again.
Great news for those of us who buy insurance 'just in case' but whilst never claiming finding the premiums keep going up. Hardly fair is it? So don't be surprised if not everyone is on your side.