Went to Kew the other day, been looking forward to it for months years , never been before. We paid extra to go on the land train thing that takes you round and the bloke did what was probably an interesting running commentary.
There were 2 yummy mummies and their 2 girls sat infront of us. The driver had said at the beginning to try and keep children quiet so people could hear.
Now I could understand babies or toddlers shrieking a bit and would let that pass but these 2 girls were 6 or 7 - old enough to know better. They talked loudly nearly the whole way round. 2 mums were too busy talking (quietly) to each other to really bother with the kids, they did a few half hearted Shuushs a couple of times but to no effect.
At that age if DD had behaved like that I'd have told her we were getting off and walking if she didn't stop and I'd have carried the threat out. As it was I hardly heard anything the driver said.
I got carried away at one point and did a Shhhh myself and one of the mums turned round and I had to glare at DD and pretend I was shusshing her. 
I probably am being an unreasonable, crotchy cow but other peoples' lack of consideration for others winds me up more and more these days.