We asked that only those with their property under offer viewed ours. It made no difference, though, as the useless estate agent just asked them.
One couple, in particular, seemed to be gathering ideas for how to update their own place - very annoying.
Another chap turned out to be a friend of the agent, just there to boost the number of viewers, I believe.
I did wonder if he was due to make a low offer, too, so we'd decide to reduce the asking price. Of course, the agent was pushing that idea - as they go for quick turnover, rather than best offer.
We sacked the agent, then sold independently for a lot more.