Supermarkets here tend to reduce perishable items at the start of the 'best before' day. They then go back on the shelf with a standard 35% off sticker on them. Same goes for M&S. Nobody has these huge last-minute discounts.
We do this, too but if we've still got stuff left at about 6pm then they get further reduced, and then again to final reductions at 8:30/9pm because we'd rather sell it for pennies than have to throw it out (especially when it'll still be perfectly fine to eat for the next few days) just because it's at the end of it's permitted shelf life and people don't want to buy it at 65% of full price.
I live in the Lake District so as we're quite rural there's a lot of animal charities, stables and farms based near our store, so you'll get their staff coming in a few times a week to buy whatever fruit/veg is on final markdwn for the animals, but - esp the charities - they have to stretch their, often very limited, budgets. Only last week there was a mix up with deliveries and our produce department got an extra stock - cucumbers, lettuce, tomatos, broccoli, mushrooms, carrots, the lot - compared to normal so they had to mark it all down to final reductions, most for less than 10p, just to get rid of it ... one of the local animal sanctuaries came in and spent £70 on 294 reduced items that would keep the animals going for the next week (I only know the number because it hit the magical "upper limit of items in a single transaction" limit that I have never reached before) ... if it was all full price it would have cost easily ten times that, which they could never afford to spend every week!
The problem comes from people who know about the reduction cycles and will lurk, not because they need the discount, but because they just want to buy a bargain for the sake of it. Like the two guys in my story earlier, they would come in every day and just take everything that was in the final reduced section, regardless of what it was, just because it was there and you knew they'd be back to do the same thing the following day too. You'd hear them at the checkout actually saying things like "What is that you've got there? Oh, you don't like them, me neither!" and so many times I'd have to bite my tongue not to say "Well if neither of you like it, put it back for someone who a) does and b) can't afford to pay full price!"