We have almost flexible hours - if I use up 1.5 to 2 hours at lunch then I make it up by either coming in earlier or staying a bit later (normal). As long as I do my 37.5 hours a week my boss doesn't mind. I started running at lunchtime because there are several men in my current team who take long lunches to play football, squash, go to the gym so there is precedent and I'm not the only one so nobody bats an eyelid. I'm hoping the same will be true of the next team I move to but I think people have just got used to seeing me going out/coming back from a run and know its something I do, luckily work commitments tend not to get in the way at the minute.

I think for me about 8 miles is as much as I could comfortably fit in at lunchtime until I sort out my faffing issues!